Enzymes

An enzymes can be defined as a protein produced by living cells, which is capable of catalysing a chemical reaction to yield specific products in other words, an enzyme is a biological catalyst. Their role is very large. So, academic Pavlov was saying: “ The enzymes are the center of biological and medical knowledge “. Braunsthein said: “All modern biochemistry speaks on enzyme’s language”.

The word enzyme means “derived from yeast” and was used when the catalytic properties of the yeast were discovered. A catalyst is an agent which in small amounts increases the velocity of a reaction without appearing in the final products of the reaction.

The substance on which an enzyme acts is called its substrate. The names of enzymes usually end is “ase” which is preceded by the name of its substrate. Many enzymes have been crystallized in pure form (now near 2500): urease was the first enzyme to be crystallized in 1926 by Sumner. The enzymes can bring about chemical reaction in body tissues or even in vitro at comparatively low temperature and low dilutions.

Mechanism of enzyme action

Enzymes decrease the energy of activation of reaction by the way of the formation enzyme-substrate complex. The velocity of reaction depends on the quantity of molecules, which level of free energy of activation more than energetic barrier. So, 2H2O2à2H2O + O2/ the energy of activation of this reaction is 75 kJ/mol. When Pt is used as catalyst the level of energy of activation of this reaction is decreased and equal 54kJ/mol. When the enzyme catalyze this reaction the energy of activation is decreased and equal 18kJ/mol.

The formation of enzyme-substrate complex

There are 3 steps in this process –

1. The formation of complex enzyme-substrate (by the weak bonds)

2. the occurrence of reaction with substrate (cleavage or formation of bonds< formation of products), formation of complex enzyme-products of reaction

3. the discharge of products from enzyme

<== попередня сторінка	\|	наступна сторінка ==>
Structure of RNA	\|	Common properties of enzymes

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