PROPERTIES OF ENZYME

There are following properties of enzymes.

  1. Globular proteins

Most of enzymes are globular protein. A few enzymes like ribo4mes are nucleic acid in nature. Globular protein of enzymes have tertiary configuration. Globular structure is very important for proper functioning of enzyme.

  1. Catalytic Properties

Enzymes influence the speed of chemical reactions. They are not utilized or consumed in the chemical reaction. So they do not appear in the end products of the reaction. An enzyme cannot start the reaction. It can only speed up the reaction. A very small quantity of the enzyme can catalyze a large quantity of the substrate and at a great speed. The effectiveness of an enzymic reaction is expressed in form of turnover number. The number of substrate molecules on which one enzyme molecule acts in one second is called turnover over number. The number for sucrose is 105 and for catalases 106.

  1. Lowering the Activation of Reaction

Activation energy is the minimum energy that is required to start a reaction. Enzyme lowers the activation of energy. The reaction can take place in the absence of enzyme. But it needs higher amount of activation energy.

  1. Specificity of Enzyme Action

Enzymes are specific in their action. The specificity of enzymes is due to their primary amino acid sequence. A given enzyme can act only on a particular substrate or a particular group of substrates. An enzyme is thus specific for both the substrate and the type of reaction that it catalyses. Thus, sucrase acts upon sucrose (cane-sugar) and lactase on milk-sugar (lactose) Sucrase will not act upon other sugars.

  1. Reversibility of Enzyme Action

The majority of reactions catalyzed by enzymes are reversible. Thus an enzyme can speed up a reaction in both directions. Thus the system attains a state of equilibrium in a short time. In the guard cells of the stomata the enzyme starch phosphorylase converts starch and inorganic phosphate into glucose monophosphate. The reaction is reversible. The same enzyme converts glucose monophosphate into starch and inorganic phosphate.

The direction of the reaction depends upon several factors. It depends on p1-1 and chemical potential of both the reactants. When the chemical potential of the products is less than that of the reactants then the reaction takes place only in one direction.

Synthesis of starch, proteins and fats are unidirectional irreversible enzymatic reactions. Such reactions have two different sets of enzymes. One enzyme is used for the synthesis of these compounds and the other is used for their breakdown.


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  1. Product Inhibition

The accumulation of products of the reaction can inhibit the enzymatic activity. The effect is very important for cell. It is a self regulating mechanism of reaction rates. It maintains the concentration of the product in a cell at a suitable level.

  1. Allosterism

Some enzymes have specific allosteric site for binding of certain effectors. It is called allosteric site. The binding of effector causes change in the structure of enzyme. This phenomenon is called Allosterism. Allosterism is shown by many enzymes.

  1. Sensitivity of Enzymes

Enzymes are sensitive to following factors

(i)  High temperature: Enzymes are sensitive to heat. The activity of enzymes increases with the increase of temperature up to 50°C. There is initial rise in the activity of enzymes above this temperature. But this is soon followed by a decline in activity. The enzymes are denatured at 70-100°C. Some enzyt: can withstand temperature of I00-120°C for long periods in dry c Jriditions. Such conditions are present in spores and dry seeds.

(ii)Low temperature: Enzymes are also se ,sitive to low temperatures. They are inactivated but not destroyed at 0°C or below.

(iii)Radiations: Enzymes are also destroyed by radiations of lower wavelengths such as ultraviolet rays and X-rays.

(iv) pH: Each enzyme has an optimal pI-I. Its activity slows down with an decrease or increase in the p11. Generally. catalases show optimum activity in a neutral medium. Amylase acts best in neutral or slightly acidic medium. Sucrase and lipase act in acid medium and trypsin act in alkaline medium.

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