What are different classes of enzymes? Explain any two with the type of reactions they catalyse.

Explanation

Enzymes are divided into six classes each with 4-13 sub-classes and named accordingly by a four-digit number.
(i) Oxidoreductases/dehydrogenases These enzymes take part in oxidation and reduction or transfer of `e^(-)`. S (reduced)+ S' (oxidised) `rarr` S (oxidised)+ S' (reduced)
(ii) Transferaes These enzymes transfer a functional group from one molecule to another (other than hydrogen). The chemical group transfer does not occur in free state.
`S-G+S'overset("Transferase")rarrS+S'-G`
(iii) Hydrolases These enzymes catalyse the hydrolysis of bonds like ester, ether, peptide, glycosidic C-C, C-halide, P-N etc.
`underset("Maltose")underset()(C_(12)" "H_(22))" "O_(11)+H_(2)Ooverset("Maltase")rarrunderset("Glucose")underset()(2C_(6)H_(12)O_(6))`
(iv) Lyases These enzymes causes cleavage, removal of groups without hydrolysis and addition of groups to double bonds or removal of groups producing double bond.
`overset(X)overset(|)C-overset(Y)overset(||)Coverset("lyase")rarrX-Y+C=C`
(v) Isomerases These enzymes cause rearrangement of molecular structure to effect isomeric changes. They are of three types. i.e., isomerases, epimerases and mutases.
`underset("(Aldose to ketose group or vice-versa)")underset()("Glucose-6-phosphat"eoverset("Isomerase")rarr"Fructose 6- phosphate")`
`underset("(Shifting the position of side group)")underset()("Glucose-6-phosphat"eoverset("Mutase")rarr"Glucose 1- phosphate")`
`underset("(Change in position of one constituent or carbon group)")underset()("Xylulose 5-phosphat"eoverset("Epimerase")rarr"Ribulose-5-phosphate")`
(vi) Ligases are enzymes catalysing bonding of two chemicals with the help of energy obtained from ATP resulting formation of bonds such as C-0, C- S, C-N and p-O e.g., pyruvate carboxyl use
`underset("pyruvate carboxylase")underset()(Ab+CrarrA-C+b)`
`"Pyruvric acid" +CO_(2)+ATP+H_(2)OhArr"Oxaloacetic"+ADP+"Pi-"`