Enzyme and mechanism for enzyme actions
Enzymes are the chemical catalysts that control verious biochemical reactions, without themselves being changed or utilized in the living beings .
Beadle(1948) define enzyme as indispensable compound that play a key role in metabolism by bringing direction and control to the physiological process of living cells.Any change in enzyme component of living cell is immediately reflected changed in the physiological and biochemical process of cell.
According to Fairley and Kilgour(1966) biological catalysts are called enzyme and with no known exception ,all enzymes are protein.
Devlin(1970) also define the enzymes as organic catalysts which increase the rate of biochemical reactions.All enzymes are protein ,but all proteins are not enzyme .
Most of the enzymes produced by all,function within that cell and hence are called intracellular or endoenzymes .However some enzyme are released by living cells and catalize reaction in the cell environment such enzyme are known as extracellular or exo enzymes.In certain cases the enzymes exist as inactive precursors called pre enzyme or pro enzyme or zymogens.These may be activated when come in contact with some activating agents conmonly known as kinase.
Protein nature of enzymes:
Dixon and web(1962) define enzyme nature as the nature of protein.The stated "enzyme is a protein with catalytic properties due to its power of specific activation."The following evidence clearly suggested protein nature of enzymes
1.Like protein ,enzyme also do denaturation in unfavourable conditions.
2.Like protein, enzyme behave as ampholytes in a electric fields .
3.Basically enzyme shows usual propettion of carbon ,hydrogen , nitrogen and sulphur as found in protein.
4.Some crystalline enzyme yield ammino acid on hydrolysis.
5.Enzymes, like protein are also involved in the antibodies formation .
Mechanism of enzyme action are explained by two theories
Lock and key model:
This model was purpose by a german chemist Emil Fischer in 1998.According to this model , the formation of enzyme substrate complex during enzyme action is analogous to the fitting of lock key.It is believed that the enzyme and substrate both have strictly complementary which during complex formation fit to each other like a specific key in the particular lock.Such structurs of enzyme are called active site in which the complementary structures of substrate get fit in .The enzyme complex dessociate into products and the enzyme become free and available for the another reaction .
This model was purposed by D.koshland(1966) According to this model the enzyme and substrate do not have strictly complementary structure but the enzyme has flexible active site structure which are changed according to substrate configuration .Thus the enzyme shows induced fit mechanism during enzyme substrate complex formation .This type of model can be compared with hand and gloves .The same gloves can be fit in the hand of many persons .In other words the gloves adjust itself in the hand of those person who bear it.
Beadle(1948) define enzyme as indispensable compound that play a key role in metabolism by bringing direction and control to the physiological process of living cells.Any change in enzyme component of living cell is immediately reflected changed in the physiological and biochemical process of cell.
According to Fairley and Kilgour(1966) biological catalysts are called enzyme and with no known exception ,all enzymes are protein.
Devlin(1970) also define the enzymes as organic catalysts which increase the rate of biochemical reactions.All enzymes are protein ,but all proteins are not enzyme .
Most of the enzymes produced by all,function within that cell and hence are called intracellular or endoenzymes .However some enzyme are released by living cells and catalize reaction in the cell environment such enzyme are known as extracellular or exo enzymes.In certain cases the enzymes exist as inactive precursors called pre enzyme or pro enzyme or zymogens.These may be activated when come in contact with some activating agents conmonly known as kinase.
Protein nature of enzymes:
Dixon and web(1962) define enzyme nature as the nature of protein.The stated "enzyme is a protein with catalytic properties due to its power of specific activation."The following evidence clearly suggested protein nature of enzymes
1.Like protein ,enzyme also do denaturation in unfavourable conditions.
2.Like protein, enzyme behave as ampholytes in a electric fields .
3.Basically enzyme shows usual propettion of carbon ,hydrogen , nitrogen and sulphur as found in protein.
4.Some crystalline enzyme yield ammino acid on hydrolysis.
5.Enzymes, like protein are also involved in the antibodies formation .
Mechanism of enzyme action are explained by two theories
Lock and key model:
Induced fit model:
This model was purposed by D.koshland(1966) According to this model the enzyme and substrate do not have strictly complementary structure but the enzyme has flexible active site structure which are changed according to substrate configuration .Thus the enzyme shows induced fit mechanism during enzyme substrate complex formation .This type of model can be compared with hand and gloves .The same gloves can be fit in the hand of many persons .In other words the gloves adjust itself in the hand of those person who bear it.
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