Enzymes (Definition, characteristics, mechanism action, activity, stability) By Saad Bin Hasan

Definition of enzyme, characteristics of enzyme, function of enzyme, mechanism action of enzyme, differences between enzyme and catalyst, activity of enzymes, stability of enzymes

1. Enzymes

2. Objectives of this study: To define enzyme To describe characteristics of enzyme To know the function of enzyme To describe mechanism action of enzyme To know the differences between enzyme and catalyst To know the activity of enzymes To know the stability of enzymes

3. Introduction to Enzyme Enzymes are protein that speed up the rate of the chemical reaction. They are like any catalyst and are not consumed in chemical reactions, nor do they alter the  equilibrium of a reaction . A small quantity of enzyme can bring about the decomposition of large amount of the substrate.

4. Introduction to Enzyme Their action is highly specific, i.e. a particular enzyme can bring about a particular reaction. An enzyme is most reactive at a particular temperature, called optimum temperature. Enzymes like other catalysts are influenced by the presence of other substances, called co-enzymes acts as promoters. They do not take part in the reaction.

5. Introduction to Enzyme They are destroyed by the ultra violet light and by heat. At temperatures to low (0`C) and too high (70-80`C) the enzymes are most inactive. They bring about many complex reactions, e.g. oxidation, reduction, hydrolysis etc.

6. Function of Enzyme The basic function of an enzyme is to increase the rate of the reaction. Enzymes act specifically with only one reactant (called a substrate) to produce product. Enzymes are regulated from a state of low activity to high activity and vice versa.

7. Mechanism Action of Enzyme Substrate approaches active site . Enzyme-substrate complex forms. Substrate transformed into product. Products released. Enzyme recycled.

8. Active Site The area of an enzyme that binds to the substrate structure has a unique geometric shape that is designed to fit the molecular shape of the substrate. Each enzyme is substrate specific. Thus the active site that is complementary to the geometric shape of a substrate molecules.

9. Lock and Key model Proposed by EMIL FISCHER in 1894 The enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another. There is no change in active site before and after a chemical reaction. Amino acid groups in the active site help substrate bind.

10. Differences Between Enzyme and Catalyst Catalyst Enzyme Catalysts are substances that increase or decrease the rate of a chemical reaction but remain unchanged. Enzymes are proteins that increase rate of chemical reactions converting substrate into product. Low molecular weight compounds. High molecular weight globular proteins. There are two types of catalysts – positive and negative catalysts There are two types of enzymes - activation enzymes and inhibitory enzymes.

11. Differences Between Enzyme and Catalyst Catalyst Enzyme Catalysts are simple inorganic molecules. Enzymes are complex proteins. Inorganic catalyst. Organic catalyst or bio catalyst. Reaction rates t ypically slower. Reaction rates several times faster.

12. Differences Between Enzyme and Catalyst Catalyst Enzyme They are not specific and therefore end up producing residues with errors Enzymes are highly specific producing large amount of good residues C-C and C-H absent C-C and C-H present Ex: vanadium oxide Ex: amylase, lipase Similarities Lowers a ctivation energy. Lowers a ctivation energy.

13. Enzyme Activity Enzyme activity is a measure of the quantity of active enzyme present. Enzyme activity = moles of substrate converted per unit time = rate × reaction volume. The SI unit of enzyme activity is the  katal . 1 katal = 1 mol s −1

14. Stability of Enzymes Enzyme Stabilization is gaining importance due to the wide range of enzyme applications. Other than medical research, they can be used in food, chemical and pharmaceuticals industries. To use these biocatalysts called enzymes to their full potential, it is very important to achieve progess in enzyme stabilization.

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