ITP 210 Kimia Pangan PROTEIN

Materi Kuliah Pokok Bahasan TIK Sub Pokok bahasan Protein Mahasiswa mampu menjelaskan struktur serta fungsi asam amino dan protein, termasuk enzim Struktur kimia asam amino dan protein Sifat fisikokimia asam amino dan protein Klasifikasi protein Denaturasi protein Sifat fungsional protein Enzim (tatanama dan spesifisitas enzim)

Protein Makromolekul (polipeptida) yang tersusun dari asam amino yang dihubungkan satu sama lain dengan ikatan peptida. Sumber: Nabati (kedelai, kacang-kacangan, dsb) Hewani (daging, ikan, unggas, dsb) Merupakan molekul yang besar, mengandung lebih dari 100 residu asam amino. Jenis: globular, fibrous, conjugated

Protein Fungsi bagi tubuh: 1 g/kg BB/hari Pengatur Pembangun Aktivitas biologis (hormon, enzim dll) 1 g/kg BB/hari

Protein Function Enzymes Catalytic activity A  B Transport Proteins Bind & carry ligand molecules (hemoglobins) Storage Proteins Ovalbumin, ferretin, casein Contractile Proteins Can contract, change shape (actin & myosins) make up elements of cytoskeleton & muscles Structural Proteins Provide support: collagen fibers of tendons, elastin of ligaments, keratin of hair & feathers, fibroin of silk & spider webs Defensive Proteins Provide protection: antibodies (IgG), fibrinogen, thrombin, and snake venoms Regulatory Proteins Regulate metabolic processes: includes hormones, transcription factors & enhancers

Protein Content in Foods Animal origin Protein (%) Plant origin Milk Rice, whole 7.5-9.0 Whole, dried 22-25 Rice, polished 5.2-7.6 Skimmed, dried 34-38 Wheat, flour 9.8-13.5 Beef Corn meal 7.0-9.4 Dried 81-90 Potato 10-13 Roasted 72 Soybean 33-42 Egg Peanut 25-28 35 Tapioca 1.3 Whole, dried, defatted 77 Chickpea 22-28

Asam amino Senyawa organik yang mengandung 2 gugus fungsional: Amin (-NH2): Bersifat basa Karboksil (-COOH): Bersifat asam Kedua gugus fungsional tersebut terikat pada karbon (-karbon) -C bersifat asimetrik (kecuali glisin): bersifat optik aktif Struktur dapat dinyatakan sebagai struktur ion dipolar. Bersifat amfoterik: dapat berperilaku sebagai asam atau basa.

Asam Amino Terdapat 20 jenis asam amino, yang berbeda satu sama lain pada gugus R yang terikat pada -karbon Gugus R dapat bersifat gugus alifatik non-polar, gugus alifatik polar, gugus aromatik, dan bermuatan positif/negatif. Asam amino yang paling sederhana: glisin (gugus R adalah H)

A theoretical amino acid Variable A theoretical amino acid Base -C bersifat asimetrik (mengingat gugus yang berbeda, yaitu –COOH, -NH2, H dan R Kecuali pada Glisin, R-nya adalah H

R-group or side chain carbon a- hydrogen a- amino a- carboxyl group Struktur Ion Dipolar R-group or side chain a- carbon a- hydrogen a- amino group carboxyl group

Kelompok Asam amino Berdasarkan Sifat Kepolaran Non-polar, R gugus alifatik Gugus R tersusun dari gugus hidrokarbon yang bersifat hidrofobik. Glisin, alanin, valin, leusin, metionin, isoleusin R gugus aromatik Gugus R tersusun dari struktur cincin aromatik atau sulfur Fenilalanin, tirosin, triptofan Polar, gugus R tidak bermuatan Gugus R mengandung gugus hidroksil atau gugus amino Bersifat hidrofilik (dapat membentuk ikatan hidrogen) Serin, treonin, sistein, prolin, asparagin, glutamin

Kelompok Asam amino Berdasarkan Sifat Kepolaran R bermuatan positif Gugus R mempunyai gugus amide yang dapat membentuk ion positif pada pH di bawah 7.0 Lisin, arginin, histidin R bermuatan negatif Gugus R mempunyai gugus COOH yang dapat membentuk ion negatif pada pH di atas 7.0 Asam aspartat, Asam glutamat

Struktur dan Singkatan 20 Asam Amino L-Alanine (Ala / A) L-Arginine (Arg / R) L-Asparagine (Asn / N) L-Aspartic acid (Asp / D) L-Cysteine (Cys / C) L-Glutamic acid (Glu / E) L-Glutamine (Gln / Q) Glycine (Gly / G) L-Histidine (His / H) L-Isoleucine (Ile / I) L-Leucine (Leu / L) L-Lysine (Lys / K)

Struktur dan Singkatan 20 Asam Amino L-Phenylalanin (Phe / F) L-Methionine (Met / M) L-Phenylalanin (Phe / F) L-Proline (Pro / P) L-Serine (Ser / S) L-Threonine (Thr / T) L-Tryptophan (Trp / W) L-Tyrosine (Tyr / Y) L-Valine (Val / V)

Sifat ionisasi Asam amino Di dalam larutan, asam amino terionisasi dan dapat bersifat sebagai asam atau basa (bersifat amfoter). Dalam keadaan dipolar (zwitterion), dimana gugus amin dan karboksil berionisasi, asam amino memiliki kelarutan yang minimal. Titik isoelektrik: pH pada saat molekul asam amino tidak bermuatan pK: pH pada saat gugus amino dan karboksil 50% terionisasi dan 50% tidak terionisasi.

Titik Isoelektrik Asam Amino pI Gly 6.0 Phe 5.5 Ala Tyr 5.7 Val Trp 5.9 Leu Asp 3.0 Ile Glu 3.2 Ser Asn 5.4 Thr 5.6 Lys 9.7 Cys 5.0 Arg 10.8 Met Gln Pro 6.3 His 7.6

Electrical Charges Some individual amino acid residues in a protein have the potential to be charged electrically in different ways, depending on the pH of the medium in which the protein is found. The individual protein molecules are said to be amphoteric, because they have the potential to function as either acid or a base, depending on the pH. Isoelectric point: when the number of positive and negative charges are equal. Protein has minimum solubility at the isoelectric point.

Ionisasi Asam Amino R H NH3+ C COO- R H NH2 C COO- + H+ R H NH3+ C (Zwitterion)

Ionisasi glisin pada berbagai nilai pH; Contoh NH3+ C COOH pH ~ 1 COO- pH ~ 6 NH2 pH ~ 11 OH- H+

Kurva Titrasi Asam Amino pI pK2 pK1 R-CHCO2H NH3+ R-CHCO2- NH2 Ekuivalen basa (OH-) pH

Polimerisasi Jenis polimerisasi: Dipeptida: 2 asam amino berikatan Oligopeptida: Polipeptida: Protein: Dihubungkan satu sama lain dengan ikatan peptida

Ikatan peptida Ikatan peptida merupakan ikatan kovalen yang menghubungkan antara gugus amin (-NH2) pada AA1 dengan gugus karboksil (-COOH) pada AA2 Pada saat terbentuk ikatan peptida, 1 molekul air dibebaskan (polimerisasi kondensasi) Ikatan peptida lebih pendek dan lebih kuat daripada ikatan C-C, tetapi lebih lemah dibanding C=C. Ikatan peptida tidak dapat berotasi secara bebas

Ikatan peptida

Pembentukan Ikatan Peptida Untuk membentuk struktur Protein/peptida

Reaksi Pembentukan Peptida

Struktur Peptida hasil polimerisasi

Bonds Between Protein Chain Bond Type Functional groups involved Disrupting solvents Electrostatic: -COO-+NH3- Carboxyl Amino Salt solutions High or low pH Hydrogen bond -(C=O)NH HO- Hydroxyl, Amide, Phenol Urea solutions Hydrophobic bonds Long aliphatic chain, aromatic Detergents, organic solvents Disulfide bonds -S-S- Cystine Reducing agents, sulfite, marcapto-ethanol

Protein Structure Primary sequence Linear sequence of AA's from N-terminal to C-terminal NCC-NCC-NCC-NCC-NCC-NCC-NCC-NCC Secondary structure Regular, recurring orientations of AA's in a peptide chain due to H-bonds = alpha helix  & beta sheets Tertiary 3D - conformational shape due to weak electrostatic interactions with other atoms Shape of most proteins  is GLOBULAR Quaternary 2 or more different polypeptides or sub-units interacting to give a unique 3D spatial relationship

Protein Structure

Struktur Protein Struktur primer (ikatan peptida)

Struktur Protein

Struktur Primer

Struktur Protein Struktur sekunder (ikatan hidrogen) -heliks protein β-sheet protein sutera

Struktur Protein Struktur tersier (disebabkan adanya ikatan hidrogen, ikatan garam, interaksi hidrofobik, dan ikatan disulfida)

Struktur Protein Struktur kuartener (agregat beberapa unit protein/ terdiri dari beberapa rantai polipeptida)

Struktur Kuartener

Types of Protein Globular protein: native proteins that are rather spherical in the configuration of their tertiary structure. Exp. Albumin (egg), globulin (meat, legume), histone (glandular tissue), protamines (fish sperm cells) Fibrous protein: Insoluble, elongated protein molecules. Exp. Collagen, elastin (in meats, poultry) Conjugated protein: proteins combined with some other type of compound, such as a carbohydrate or lipid. Exp: mucoproteins (glycoproteins), lipoprotein, metalloprotein, nucleoprotein, phosphoprotein

Example of Food Protein in Structures and shapes Food Proteins Protein Structure Protein shape Egg albumin Globular Spherical Meat and legume globulins Globular Spherical Collagen Fibrous Elongated Elastin Fibrous Elongated Glycoprotein: ovomuvoid Conjugated Protein bound to carbohydrate and hemagglutinin Lipoprotein: chylomicron Conjugated Protein bound to lipid LDL and VLDL Metalloprotein: hemoglobin Conjugated Protein bound to metal ferritin and myoglobin Phosphoprotein: casein Conjugated Protein bound to phosphorus

Komponen Bahan Pangan Perubahan Yang mungkin Terjadi selama Proses Pengolahan dan Penyimpanan Pangan Protein Denaturasi (karena panas) yang akan menyebabkan perubahan kelarutan, sehingga mempengaruhi tekstur pada bahan pangan Penyimpangan flavor yang disebabkan karena oksidasi (dikatalisis oleh cahaya) Degradasi enzimatik yang akan menyebabkan perubahan pada tekstur dan flavor (bisa menyebabkan terbentuknya flavor pahit) Pembekuan dapat menyebabkan protein mengalami perubahan konformasi dan kelarutannya

Protein Denaturation Denaturation of proteins involves the disruption and possible destruction of both the secondary and tertiary structures. Since denaturation reactions are not strong enough to break the peptide bonds, the primary structure (sequence of amino acids) remains the same after a denaturation process. Denaturation disrupts the normal alpha-helix and beta sheets in a protein and uncoils it into a random shape.

Protein Denaturation Denaturation occurs because the bonding interactions responsible for the secondary structure (hydrogen bonds to amides) and tertiary structure are disrupted. In tertiary structure there are four types of bonding interactions between "side chains" including: hydrogen bonding, salt bridges, disulfide bonds, and non-polar hydrophobic interactions, which may be disrupted. Therefore, a variety of reagents and conditions can cause denaturation. The most common observation in the denaturation process is the precipitation or coagulation of the protein.

Protein Denaturation Unfolding of protein structure (due to H bonds breaking) without disrupting protein covalent bonds. Functional properties of protein will change during denaturation (e.g. enzyme function will be stopped; solubility in water will decrease). Example: Thermal processing denatures the meat protein actin, myosin and myoglobin. Cooking egg denatures egg white proteins including ovalbumin

Protein Denaturation

Factors Influencing Protein Denaturation Heat Alcohol Acid or Base Heavy metals Reducing Agents

Protein Denaturation Effect of Alcohol Hydrogen bonding occurs between amide groups in the secondary protein structure. Hydrogen bonding between "side chains" occurs in tertiary protein structure in a variety of amino acid combinations. All of these are disrupted by the addition of another alcohol. Alcohol denatures proteins by disrupting the side chain intramolecular hydrogen bonding. New hydrogen bonds are formed instead between the new alcohol molecule and the protein side chains.

Protein Denaturation Effect of Acids and Bases Salt bridges result from the neutralization of an acid and amine on side chains. The final interaction is ionic between the positive ammonium group and the negative acid group. Any combination of the various acidic or amine amino acid side chains will have this effect.

Protein Denaturation Effect of Acids and Bases Acids and bases disrupt salt bridges held together by ionic charges. A type of double replacement reaction occurs where the positive and negative ions in the salt change partners with the positive and negative ions in the new acid or base added. This reaction occurs in the digestive system, when the acidic gastric juices cause the curdling (coagulating) of milk.

Protein Denaturation Effect of Acids and Bases The denaturation reaction on the salt bridge by the addition of an acid results in a further straightening effect on the protein chain

Denaturasi Perubahan struktur sekunder, tersier dan kuartener protein Perubahan konformasi protein Struktur primer tetap → protein tidak terfragmentasi

Denaturasi Flour  Process  Bread

Functional Properties of Protein Characteristics that govern the behavior of proteins in foods during processing, storage, and preparation as they affect food quality and acceptance.

Fisiko-kimia Protein Hidrasi (daya ikat air/water holding capacity) dan pembentuk viskositas Kelarutan (penting untuk proses ekstraksi) Pengental Pembentuk gel (penting untuk produk olahan daging dan ikan) Pembentuk tekstur Koagulasi panas dan pembentuk film (seperti pada kembang tahu) Texturized protein (pembentukan struktur serat seperti daging pada produk ekstrusi)

Fisiko-kimia Protein Pengemulsi Pembentuk busa (busa protein putih telur melembutkan dan mengembangkan produk cake) Pembentuk adonan (protein gluten yang bersifat viskoelastis pada adonan roti dan mie) Bersama-sama dengan gula pereduksi membentuk warna dan aroma melalui reaksi Maillard

Typical Functional Properties Performed by Proteins in Food Systems Functional Property Mode of Action Food System Solubility Protein solvation, pH dependent Beverages Water absorption and binding H-bonding of HOH, entrapment of HOH Meats, sausages. Breads, cakes Viscosity Thickening, HOH binding Soups, gravies Cohesion-adhesion Protein acts as adhesive material Meats, sausages, baked goods, pasta products Elasticity Hydrophobic bonding in gluten, disulfide links in gels (deformable) Meats, bakery

Typical Functional Properties Performed by Proteins in Food Systems Functional Property Mode of Action Food System Gelation Protein matrix formation and setting Meats, curds, cheese Emulsification Formation and stabilization of fat emulsions Sausages, soup, cakes Fat adsorption Binding of free fat Meats, sausages, donuts Flavor binding Adsorption, entrapment, release Simulated meats, bakery, etc Foaming Forms stable film to entrap gas Whipped toppings. dessert

Factors Influencing the Functional Properties of Food Proteins Intrinsic Environmental Factors Process Treatments Composition of proteins Conformation of proteins Mono- or multi component Homogeneity – heterogeneity Water pH Temperature Oxidizing/ reducing agents Lipids. Flavors, sugars Heating Salts Reducing/ oxidizing agents Drying Physical modification Chemical modification

Functional Properties of Proteins Displayed in Interactions with Different Food Constituents Interaction With Water Water and Proteins Lipids or Gases Wet ability Swelling Rehydration Water holding Solubility Viscosity inducing Gelling Fiber forming Dough forming Membrane forming Emulsifying ability Emulsification stabilization Foaming ability Foam stabilization Influence to food materials: Appearance, color, juiceness, mouth feel, texture Cutting, mincing, mixing, formation of dough, fibers, foils, bubbles, shaping, and transporting

Aspects of protein functionality and its interrelationship BINDING PROPERTIES Protein Protein and Sorbed H2O Protein in solution TEXTURAL PROPERTIES SURFACE PROPERTIES Protein and Bound Fat Sorption Foaming Emulsification Gelation Coagulation Texturization Solubility H2O Air Energy Protein – Air Foams Protein – Lipid Emulsion Texturized Protein Fat Fat Binding Gel Coagulum H+, OH-, M+, A-

Characteristics Affected by Food Proteins Hydra- tion Swelling Water holding Wettability Solubility Visco- elasticity Appea- rance Taste Coagulation Mouthfeel Smoothness Gelation Thickening Turbidity Color Bitterness Sweetness Flavor Food Characteristics affected by Proteins

Emulsification Since protein molecules contain both hydrolytic and hydrophobic characteristics, proteins can stabilize emulsions by acting at the oil-water interface. This functional property is important in the formation of many common food products, such as salad dressings, sauces, frankfurters, and sausages. Foods, such as meat tissue, milk, eggs, and soy contain proteins that can be isolated as emulsifiers.

Protein Gelation Proteins can form a well-ordered gel matrix by balancing protein-protein and protein-solvent interactions in food products. These gel matrices can hold water, fat, and other food ingredients to produce various food products, including bread dough, communited meat products, gelatin desserts, tofu, and yoghurt.

Gelation Mechanism of Protein

Water Holding Capacity The ability of a protein molecule to bind water has to do with the presence of hydrophylic and charged groups in its structure. This property is called water-holding capacity of protein Example: meat retains water during application of external forces such as cutting, heating, grinding, and pressing. Affected by: pH, salt, and temperature.

Water Holding Capacity When the negative and positive charges on a protein equal to each other, protein : protein interactions are at maximum. When the protein is not electrically neutral, these interactions lessen, allowing for greater water: protein associations. By increasing salt concentration, more Na+ and Cl- ions are available to bind the charged groups on protein fiber molecules. This reduces the protein fiber interactions with each other in favor of increase protein fiber : water associations. As temperature increases to 80oC, water binding increases in proteins that form thermally induced gels, because gelations traps water inside a three-dimensional gel network in addition to creating gel surface binding of water molecules.

Protein Functionality: Fat Binding Properties Hydrophobic proteins effectively lower surface tension and bind many lipophilic materials, such as lipids, emulsifiers, and flavor materials. The capacity of protein to bind fat is important in the production of meat extenders and replacers, in which the absorption of fat by proteins enhances flavor retention and improves mouthfeel. Fat is absorbed through physical entrapment. Fat absorption can be increased if the protein is modified chemically to increase its bulk density.

Contribution of Amino Acids to Taste and Flavor Contribution to Taste/Flavor Amino Acids Sweet taste Gly, Ala, Thr, Pro, Ser, Glu Bitter taste Phy, Tyr, Arg, Leu, Val, Met, His Umami and Sour taste Glu, Asp Cheese and miso (soy sauce) are examples of fermented foods whose flavor is largely caused by their amino acid composition.

Protein Hydrolysis Protein molecules may undergo hydrolysis to form shorter chains. The reaction usually is the result of enzymatic action by peptidases, but sometimes collagen is cleaved by acid hydrolysis. The result if cleavage of the peptide bond and uptake of a molecule of water The shorter chains resulting from hydrolysis show increased solubility and decreased ability to thicken food products.

Degradasi enzimatik Meningkatnya kandungan peptida dan asam amino pada tempe (dikehendaki) Meningkatnya kandungan peptida pada keju karena pertumbuhan mikroba yang tidak dikehendaki pada saat pemeraman, menyebabkan keju berasa pahit.

Food Enzyme

What is enzyme? Specialized protein molecules that speed up chemical reactions in living cells (biological catalysts). Specific for particular substances Composed of 200-1000 amino acids residues covalently linked. Molecular weight: 12.000 – 1 million

Sumber Enzim Plant Animal Microbial sources Kedelai: lipoksigenase Sapi: renin Microbial sources Bakteri asam laktat: memproduksi enzim proteolitik  membantu degradasi protein keju

Some Properties of Enzymes Cofactor Small inorganic ion that helps catalyze reactions Exp. Cu+2 ; Mg+2 ; Mn+2, etc Coenzyme Small, organic, non-protein ligands (such as NAD+, B-vitamins), which catalyze reaction most often by gaining/losing electron, transfers group or break bonds. Reaction path     E + S <---> ES <---> E + P sucrase reaction Active site Portion of enzyme protein that attaches to the substrate by means of weak chemical bonds (H-bonds, ionic bonds, hydrophobic forces, etc)

How important in food processing? In foods: Indigenous food enzymes, e.g, papain in papaya Added enzyme: concentrate or isolates Enzyme produced by microorganisms and present either as contaminants or added as cultures Important in food processing because of the roles they play in the composition, processing and shelf life of foods.

How important in food processing? Desirable: Used in food processing: Papain tenderizes meat Amylase/glucoamylase is used in the production of glucose Proteases in the production of bread To measure adequacy of processing Phosphatase in milk pasteurization and catalase and peroxidase in vegetable blanching. Undesirable: Cause quality changes in food color, texture, flavor and odor during storage and use Lipases produce rancidity Polyphenol oxidase results in enzymatic browning Lipoxigenase produces off-flavor in soymilk

Examples of Several Food Enzymes Food Enzyme Reaction Amylase Hydrolysis of starch Chlorophyllase Changes color of chlorophyll Catalase Decomposition of hydrogen peroxide (H2O2) Glucose oxidase Oxidation of glucose Lactase Hydrolysis of lactose Lipase Hydrolysis of triglycerides Lipoxygenase Oxidation of unsaturated lipid Pectinase Clarification of wines; modification of jam jelly texture Peptidase Hydrolysis of proteins Polyphenol oxidase (PPO) Browning of fruits and vegetables Proteases Elimination of chill haze on cold meat packaging; meat tenderizers Rennet Coagulation of milk protein Sucrase Hydrolysis of sucrose

Bau Langu (Beany Flavor) Disebabkan enzim lipoksigenase yang aktif dengan penghancuran jaringan Enzim lipoksigenase menghidrolisa asam lemak tidak jenuh menghasilkan senyawa volatil. Pencegahan : pemanasan untuk inaktivasi lipoksigenase, pH rendah untuk penghambatan aktivitas enzim, ekstraksi lemak

Characteristics of starch degrading enzyme Enzymes Sources Hydrolytic activity Products -amylase Humans, animals, plants, m.o. Random from non-reducing end at -1,4 glycosidic linkage Mixture of glucose, maltose, oligosa-charides, and limit dextrins -amylase Humans, some plants, m.o. Stepwise from non-reducing end at alter-nate -1,4 glycosidic linkage Maltose and limit dextrins Glucoamylase Humans, animals, m.o. -1,4 and -1,6 gly-cosidic linkages Glucose Debraching Limit dextrinase Plants -1,6 glycosidic linkages Mixture of oligosa-charides Isoamylase Microorganisms Pullunase

Pemanfaatan Enzim di industri roti Adonan roti: kuat dan elastis yang dapat menahan gelembung gas  membentuk volume roti yang besar. Tepung terigu mengandung sedikit gula yang dapat difermentasi (0.5% mono dan disakarida)  tidak cukup untuk proses fermentasi untuk menghasilkan adonan yang baik dan volume roti yang besar. Ditambahkan -amylase untuk menghasilkan maltosa dari pati terigu digunakan oleh Sacharomyces cereviceae untuk membentuk gas CO2 dan etanol.

Amilogram

Skema pembuatan sirup fuktosa Pati Singkong & lainnya Pencairan Sirup fruktosa (42% fruktosa, 52% dekstrosa, 6% oligosakarida Pemurnian Pemekatan -amylase Sakarifikasi Glukoamilase Sirup dekstrosa Isomerase Isomerasi (dekstrosa  fruktosa)

Lysozyme The enzyme lysozyme is present in some foods such as egg white, shellfish, milk and plant tissues Lysozyme hydrolyzes the mucopeptide layer present in the cell wall of Gram positive bacteria and in the middle membrane of Gram negative bacteria The anti microbial effect is manifested by the lysis of cells

Active Site of Enzyme Active Site: the region on the surface of enzyme where catalytic occurs The active site of an enzyme is directly involved in binding and catalytic action Active site is a small, three-dimensional region that contains amino acids that bind non-covalently with the substrate. Exp. Active site of papain is adjacent histidine and cysteine residues that form non-covalent bonds with functional groups of protein substrate The location where the substrate joins with the enzyme to form enzyme-substrate complex: transition state, reaction intermediate, or ES-complex

How an Enzyme Works Substrate (S) + Enzyme (E) Enzyme (E) + Product (P) ES The green one is enzyme. Unchanged at the end of the reaction The orange one is substrate molecules acted on by the enzyme. Changed to products. The blue one is water. Involved in the reaction. Lower activation energy (the amount of energy needed to convert substrate molecules from the ground or baseline energy state to the ES complex)

Enzim vs Energi Aktivasi Transition state (pada puncak) dengan adanya enzim (ES) memi-liki energi aktivasi yang lebih rendah dibanding transition state tanpa enzim EA reaksi tanpa katalisator Keadaan akhir pada kesetimbangan EA dengan katalisator Keadaan awal Pembatas energi aktivitas Energi bebas sistem  Kemajuan reaksi 

How an Enzyme Works The substrate molecules (orange rectangle) diffuse in [from the left] and, as in all hydrolysis reactions, water (represented by the small blue rectangle) participates in the breakdown, with the release of products (red and yellow squares), which diffuse away [to the right]. The process continues as long as there are substrate molecules to be converted, as the enzyme molecule (green) is unchanged at the end of the reaction.

Reaction Rates in Food as a Function of Water Activity Zone I Non-enzymatic browning Lipid oxidation Hydrolytic reactions Moisture content isotherm Enzyme activity Mold growth Yeast growth Bacteria growth Relative Reaction Rate Moisture Content Water Activity 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0

How to name enzyme? By adding suffix “ase” to the name of enzyme substrate or reaction. For example: Urease: acts on urea Glucose oxidase oxidizes glucose to gluconic acid By adding suffix “in” to the name of enzyme source. For example: Papain is obtained from papaya plant

International Commission of Enzyme Develop a systematic nomenclature and classification scheme for enzyme. Trivial name, systematic name, enzyme commission (EU) number, specific reaction. For example: amylase Trivial name: -amylase Systematic name: -1,4-Glucan-4-glucanohydrolase EC number: 3.2.1.1 Reaction: hydrolysis of -1,4-glucan links Enzyme is divided into six classes based on types of reactions they catalyze: Oxidoreductase (1); Transferase (2); Hydrolase (3); Lyase (4); Isomerase (5); Ligase (6)

Enzim Dalam Pengolahan Pangan Dua kelompok enzim yang banyak digunakan dalam pengolahan pangan: Oksidoreduktase Hidrolase Yang jarang digunakan dalam pengolahan pangan: Liase Ligase

Oxidoreduktase (1) Enzim yang dapat mengkatalisis reaksi oksidasi atau reduksi suatu bahan. Yang utama: Oksidase: mengkatalisis reaksi antara substrat dengan molekul oksigen. Katalase, peroksidase, tirosinase, asam askorbat oksidase, lipoxidase (lipoxygenase) Dehidrogenase: enzim yang aktif dalam pengambilan atom hidrogen dari substrat. Suksinat dehidrigenase: memecah asam glutamat menjadi asam ketoglutarat dan NH3 Laktat dehidrogenase: memecah asam laktat menjadi asam piruvat.

Transferase (2) Enzim yang ikut serta dalam reaksi pemindahan (transfer) suatu radikal atau gugus (AB + C  A + CB). Yang utama: Fosforilase: memecah ikatan glikosida -1,4 pati dengan pertolongan ion fosfat membentuk -D-glukosa-1-fosfat. Transfosforilase: memindahkan gugus fosfat dari suatu molekul ke molekul lainnya, misal memindahkan gugus fosfat dari ATP kepada heksosa menghasilkan heksosa-monofosfat dan ADP.

Transferase (2) Transaminase: mengkatalisis reaksi antara asam amino  dan asam -keto menghasilkan asam amino baru dan asam keto baru. Misal reaksi antara asam glutamat dan asam oksaloasetat menghasilkan asam -ketoglutarat dan asam aspartat. Transmetilase: mengkatalisis pemindahan gugus metil dari suatu mole-kul ke molekul lainnya. Contoh: memindahkan gugus metil dari metionin kepada asam guanidoasetat membentuk homosistein dan kreatin. Transasetilase: membentuk molekul bergugus asetil.

Hidrolase (3) Mengkatalisis reaksi hidrolisis suatu substrat atau pemecahan substrat dengan pertolongan molekul air. Yang utama: Lipase: menghidrolisis ikatan ester pada lemak alami menjadi gliserol dan asam lemak. Glikosidase: menghidrolisis ikatan glikosida Aminopeptidase (tripsin): menghidrolisis ikatan peptida. Urease: menghidrolisis urea menjadi amonia dan CO2.

Liase (4) Enzim yang aktif dalam pemecahan ikatan C-C dan ikatan C-O dengan tidak menggunakan molekul air. Yang utama: Dekarboksilase: memecah ikatan C-C Karbonat anhidrase: memecah ikatan C-O

Isomerase (5) Enzim yang mengkatalisis reaksi perubahan konfigurasi molekul dengan cara pengaturan kembali atom-atom dalam molekul substrat, sehingga dihasilkan molekul baru yang merupakan isomer dari substrat, misal merubah aldosa menjadi ketosa. Yang utama: Fosfoheksosa isomerase: mengubah glukosa 6-P (glukosa 6-fosfat) menjadi fruktosa 6-P Fosfomanosa isomerase: merubah glukosa 6-P menjadi manosa 6-P

Ligase (6) Mengkatalisis pembentukan ikatan-ikatan tertentu, misalnya pembentukan ikatan C-O, C-C dan C-S dalam biosintesis ko-enzim A serta pembentukan ikatan C-N dalam sintesis glutamin.

Nomor Kode Enzim (EC) Terdiri dari 4 digit: Digit 1: Nomor urut dari salah satu 6 pembagian umum. Digit 2: Subklas, substrat, atau jenis reaksi Digit 3: Subklas, jenis reaksi yang lebih detail lagi, biasanya memerlukan NAD dan ko-enzim Digit 4: nomor seri dalam subklas tersebut.

Pedoman Klasifikasi Enzim Oksidoreduktase 1.1. Bekerja pada gugus -CHOH 1.2. Bekerja pada gugus keton atau aldehida 1.3. Bekerja pada gugus -CH-CH- 1.4. Bekerja pada gugus –CH-NH2 1.5. Bekerja pada gugus –C-NH- 1.11. Bekerja pada gugus H2O2

Pedoman Klasifikasi Enzim Tranferase 2.1. Pemindahan (transfer) gugus satu carbon seperti metil atau karboksil 2.2. Pemindahan gugus aldehida dan keton 2.3. Pemindahan gugus asil 2.4. Pemindahan gugus glikosil 2.5. Pemindahan gugus alkil 2.6. Pemindahan gugus nitrogen 2.7. Pemindahan gugus yang mengandung fosfor 2.8. Pemindahan gugus yang mengandung sulfur

Pedoman Klasifikasi Enzim Hidrolase 3.1. Bekerja pada ikatan ester 3.2. Bekerja pada senyawa glikosil 3.3. Bekerja pada ikatan ester-tio 3.4. Bekerja pada ikatan peptida 3.5. Bekerja pada ikatan C-N yang bukan peptida 3.6. Bekerja pada ikatan asam anhidrida 3.7. Bekerja pada ikatan C-C 3.8. Bekerja pada ikatan halida

Pedoman Klasifikasi Enzim Liase 4.1. Bekerja pada –C=C- 4.2. Bekerja pada –C=O 4.3. Bekerja pada C=N- 4.4. Bekerja pada –C=S 4.5. Bekerja pada C-halida

Pedoman Klasifikasi Enzim Isomerase 5.1. Rasemase dan epimerase 5.2. Cis-trans isomerase 5.3. Oksidoreduktase intramolekul 5.4. Transferase intramolekul 5.5. Liase intramolekul

Pedoman Klasifikasi Enzim Ligase 6.1. Pembentukan ikatan C-O 6.2. Pembentukan ikatan C-S 6.3. Pembentukan ikatan C-N 6.4. Pembentukan ikatan C-C

Nomenklatur enzim yang penting dalam pengolahan pangan No. EC Nama sistematiknya Nama trivial 1. Oksido-reduktase 1.1.3.4. -D-glukosa: O2 oksidoreduktase Glukosa oksidase 1.10.3.1 -difenol: 02 oksidoreduktase Katekol oksidase 1.11.1.6 H2O2: H2O2 oksidoreduktase Katalase 1.11.1.7 Donor: H2O2 oksidoreduktase Lipoksigenase/lipoksidase

No. EC Nama sistematiknya Nama trivial 2. Transferase 2.1.1.5. -1,6-glucan; D-fruktosa 2 glukosil transferase Dekstran sukrase 2.4.1.19 -1,4-glukan-4gliosil transferase Enzim B. macerans 3. Hidrolase 3.1.1.1. Karbolik ester hidrolase Karboksil esterase 3.1.1.3. Gliserol ester hidrolase Lipase 3.1.1.11 Pektin pektil hidrolase Pektin esterase 3.2.1.1. -1,4-glukan glukanohidrolase -amilase 3.2.1.2. -1,4-glukan maltohidrolase -amilase 4. Isomerase 5.3.1.9. D-glukosa-6-fosfat ketol isomerase Glukosa isomerase

Faktor yang mempengaruhi aktivitas enzim Suhu Mula-mula dengan meningkat suhu, aktifitas enzim meningkat. Tetapi, pada suhu tertentu, enzim mengalami inaktivasi. Pada suhu rendah, laju inaktivasi enzim sangat lambat pH Aktivitas maksimum: 4.5-8.0 (tergantung jenis enzim) Pada kisaran pH di luar kisaran tersebut, umumnya enzim mengalami inaktivasi. Aktivitas air Pada aw yang rendah, enzim tidak aktif. Pada aw tinggi, enzim aktif Garam Kadar elektrolit yang tinggi umumnya mempengaruhi kelarutan protein  mempengaruhi aktifitas enzim.

Pengaruh Suhu Pada suhu rendah, aktivitas enzim lambat. 20 30 40 50 60 70 10 80 100 Suhu (oC) Keaktifan (%) Pada suhu rendah, aktivitas enzim lambat. Aktivitas enzim optimum: 45-55oC Pada suhu tinggi, laju inaktivasi enzim cepat sekali, sehingga reaksi enzimatik praktis berhenti sama sekali

Pengaruh pH Enzim memiliki pH optimum yang khas, yaitu pH yang menyebabkan aktivitasnya maksimal. pH optimum: 4.5-8.0. Pada pH rendah aktivitas enzim rendah. Pada pH yang lebih tinggi aktivitas enzim menurun. pH optimum Laju reaksi Contoh: Terjadinya browning oleh enzim fenolase dapat dihambat dengan menurunkan pH larutan sampai pH 3.0, sebab pH optimal fenolase 6.5 3 4 5 6 7 8 9 10 11 12 13 Suhu (oC)

pH optimum beberapa enzim Pepsin : 1.5 Tripsin : 7,7 Katalase : 7.6 Arginase : 9,7 Fumarase : 7,8 Ribonuklease : 7,8

Enzymatic reaction vs aw At low Aw (<0.2), freely mobile water is not available to carry out the reaction, and so enzymatic reactions tend to be surpressed in the lower regions of the sorption isotherm. At high Aw, free water is available for the enzymatic reaction. For example: lipoxygenase starts to be active after dry soybean (MC=14%) is soaked in water  off-flavor

Rate of Enzymatic Reaction in Food as a Function of Water Activity Zone I Moisture content isotherm Enzyme activity Relative Reaction Rate Water Activity 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0

Pengaruh Konsentrasi Substrat terhadap kecepatan reaksi enzimatik Pada konsentrasi substrat yang amat rendah, kecepatan reaksi pun amat rendah. Kecepatan reaksi akan meningkat dengan meningkatnya konsentrasi substrat. Pada titik tertentu, peningkatkan konsentrasi substrat tidak dapat meningkatkan kecepatan reaksi (enzim menjadi jenuh oleh substratnya dan tidak dapat berfungsi lebih cepat). Pada saat kecepatan reaksi tidak berubah lagi disebut mencapai kecepatan Maksimum (Vmax)

Pengaruh Konsentrasi Substrat Terhadap Kecepatan Reaksi Enzimatik Persamaan Michaelis-Menten Vmax Konsentrasi Substrat, M  Kecepatan reaksi  ½ Vmax V = Vmax [S] KM + [S] Dimana: V = kecepatan reaksi pada konsentrasi substrat [S] Vmax = kecepatan maksimum KM = tetapan Michaelis-Menten enzim bagi substrat tertentu

Persamaan Michaelis-Menten Sudut = KM VMax 1 V [S] 1 V = KM VMax [S] +

Tugas Mandiri Buat artikel (per kelompok, max 3 orang) Aplikasi enzim dalam industri pengolahan pangan yang lain (cara penggunaan, tujuan penggunaan, mutu akhir produk yang diinginkan) : yang diinginkan Menghilangkan enzim dalam proses pengolahan pangan (mengapa, caranya, mutu akhir produk yang diinginkan): yang tidak diinginkan