Enzyme Substrate Complex

In biochemistry, substrate is a type of molecules which will act upon enzymes.  Enzymes shall catalyze the chemical reaction which includes substrate molecule. In case of reaction which includes single substrate molecule helps in easy binding of enzyme with substrate in its active site and thus the enzyme substrate complex is formed. The substrate shall be converted to one or more than one products. Thereby the products are released from active site of enzyme. The active site is free and it can accept other substrate molecules.  If more than one substrate is present, then binding of enzyme is restricted to a particular active site of substrate just before the products are released.

For instance, formation of curd that is rennet coagulation is a type of reaction which initiates after the addition of enzyme like rennin to milk. The substrate in this reaction is milk protein called casein and enzyme molecule is rennin. The two polypeptides are formed as product that is obtained as a cleavage product of substrate that has larger peptide. Another instance is the decomposition of hydrogen peroxide chemically with the help of enzymes like catalase. It is known that enzymes are catalyst in nature and are not subjected to any physical or chemical changes during the course of reaction. However the substrate is converted in to products.  For instance, hydrogen peroxide is chemically converted into oxygen gas and water molecule.

E + S ↔ ES → EP  ↔ E +P

Where E is enzyme

S is substrate

P is product

ES is enzyme substrate complex

EP is enzyme product complex

The initial and final binding of enzyme is reversible in nature.  Second binding is irreversible in nature.  If the substrate concentration is increased, rate of reaction also increases. Enzyme substrate complex may not be able to perform all reactions in human beings as it does in laboratory.

Questions:

• What is enzyme substrate complex?
• What is significance of enzyme substrate complex?
• Give some instance for enzyme substrate complex.