INTRODUCTION OF ENZYMES

 

INTRODUCTION OF ENZYMES

An enzyme is a specialized protein produced with an organism which is capable of catalyzing a a specific chemical reaction. Since the enzyme act as a catalyst, it is also called a biocatalyst. A catalyst influences the rate of a chemical reaction, usually without undergoing any change itself so in this respect an enzyme differ from a normal catalyst.

STRUCTURE OF ENZYMES

All enzymes are proteins which are which are high molecular weight macromolecules. An enzymes may consist of a single polypeptide chain or a cluster of polypeptide chain. A polypeptide chain is made up of number of amino acid units linked by peptide bonds.

            The sequence and number of the 20 amino acids which make up enzyme varies in different enzymes. This arrangement of enzymes is specific for a particular enzyme and determines the properties of the enzyme. The polypeptide chain has an amino (-NH₂) terminal and a carboxyl (-COOH) terminal biosynthesis of the enzyme begins at amino terminal.

                                                           structure of an enzyme

ACTIVE SITE

An enzyme has a distinct cavity or cleft in which the substrate is bound. A substrate is a specific compound acted upon by an enzyme. The part of the enzyme where the substrate blinds is called the active site (since that is where the catalytic “action” happens).

For example:                      CO₂          +        H₂O             -------- H₂CO₃

                                   Carbon dioxide         water                carbonic acid

In the absence of the enzyme carbonic anhydrase this reaction is very slow, producing two hundred molecular of carbonic anhydrase in an hour but in the presence of carbonic anyhydrase present in the cytoplasm, this reaction speeds up dramatically with roughly six lakhs molecules formed every second.

NATURE OF ENZYME REACTION

As we already know that an enzyme has a distinct cavity in which substrate bounds. The cleft contains an active centre in which amino acids are grouped together in such a way as to enable them to combine with substrate; it is the chemical which convert in to a product. Thus enzymes include active sites which are capable of converting substrate (S) in to a product (P).

 

S-------------P

                                                      (Substrate)      (Product)

 

01.The substrate ‘S’ bind to the active site of the enzyme for which it has to diffuse towards the active site. There is the formation of ‘ES’ complex. This complex formation lasts for a short time and is called transient phenomenon.

02.When substrate binds to the active site of enzyme a new structure of the substrate called transition state structure is formed.

03.The molecules of the substrate grouped undergo chemical changes, breaking or making of bonds and finally the product is formed and is released from the active site.

04.The pathway of this transformation of substrate into product must go through the so called transition state structure.

05.The molecule of the substrate grouped undergo chemical changes, breaking or making of bonds and finally the product is formed and is released from the active state.

06.The pathway of this transformation of substrate in to product must go through the so called transition structure. There can be altered structural state between the stable substrate and the product. In this changes of substrate to product, all intermediate structural states are unstable.