INTRODUCTION

ENZYMES

Definition.

Enzymes are the most important group of proteins which are biologically active. They tremendously increase the efficiency of a biochemical reaction and are specific for each type of reaction.

Importance

Without these enzymes the reaction would proceed at a very slow speed making life impossible. Composition.

Enzymes are composed of hundreds of amino acids. These amino acids are brought closer and are arranged in a specific way by coiling and folding of the polypeptide chain within the globular symmetry of the enzyme

Active Site. The catalytic activity is restricted to a small portion of the structure known as the active site.

Substrate. The reactant called substrate is attached to the active site and converted into product. Active site consisting of only a few amino acids. While rest of the bulk of the amino acids maintains the globular structure of the enzyme.

Cofactors.

Definition.

Some enzymes consist solely of proteins. Others also have a non-protein part known as a co-factor, which is essential for the proper functioning of the enzymes. Functions.

• The cofactor usually acts as “bridge” between the enzyme and its substrate,

• It contributes directly to the chemical reactions which bring about catalysis.

• Sometimes the co-factor provides a source of chemical energy, helping to drive reactions which would otherwise be difficult of impossible.

Substrate molecules will not fit correctly at the active centre and there will be no catalytic action unless the cofactor molecule is also present.

Activators.

Definition.

Some enzymes use metal ions (Zn+2, Fe+2 Mg+2 etc.) as co-factors and this detachable co-factor is known as an activator if it is an inorganic ion.

Prosthetic Group.

Definition.

If the non-protein part is covalently bonded, it is known as a prosthetic group.

Example.

Cytochrome enzymes use haem group as prosthetic group.

Coenzymes.

Definition.

If it is loosely attached to the protein part it is known as coenzyme. It is closely related to vitamins, which represent the essential raw materials from which coenzymes are made.

Only small quantities of vitamins are needed because, like enzymes, co-enzyme can be used again and again.

Examples

 Nicotinamide Adenine dinucleotide (NAD).

 Flavin Adenine dinucleotide (FAD)

INTRODUCTION

ENZYMES

Definition.

Enzymes are the most important group of proteins which are biologically active. They tremendously increase the efficiency of a biochemical reaction and are specific for each type of reaction

Importance

Without these enzymes the reaction would proceed at a very slow speed making life impossible. Composition.

Enzymes are composed of hundreds of amino acids. These amino acids are brought closer and are arranged in a specific way by coiling and folding of the polypeptide chain within the globular symmetry of the enzyme.

Active Site. The catalytic activity is restricted to a small portion of the structure known as the active site.

Substrate. The reactant called substrate is attached to the active site and converted into product. Active site consisting of only a few amino acids. While rest of the bulk of the amino acids maintains the globular structure of the enzyme.

Cofactors.

Definition.

Some enzymes consist solely of proteins. Others also have a non-protein part known as a co-factor, which is essential for the proper functioning of the enzymes.

Functions.

• The cofactor usually acts as “bridge” between the enzyme and its substrate,

• It contributes directly to the chemical reactions which bring about catalysis.

• Sometimes the co-factor provides a source of chemical energy, helping to drive reactions which would otherwise be difficult of impossible.

Substrate molecules will not fit correctly at the active centre and there will be no catalytic action unless the cofactor molecule is also present.

Activators.

Definition.

Some enzymes use metal ions (Zn+2, Fe+2 Mg+2 etc.) as co-factors and this detachable co-factor is known as an activator if it is an inorganic ion.

Prosthetic Group.

Definition.

If the non-protein part is covalently bonded, it is known as a prosthetic group.

Example. Cytochrome enzymes use haem group as prosthetic group.

Coenzymes.

Definition.

If it is loosely attached to the protein part it is known as coenzyme. It is closely related to vitamins, which represent the essential raw materials from which coenzymes are made. Only small quantities of vitamins are needed because, like enzymes, co-enzyme can be used again and again.

Examples

 Nicotinamide Adenine dinucleotide (NAD).

 Flavin Adenine dinucleotide (FAD)