This document discusses the nomenclature and classification of enzymes. It begins by defining enzymes as biocatalysts produced by living cells that catalyze biochemical reactions in animals and plants. Enzymes are generally named based on their substrate, with the suffix -ase added to the end of the substrate name. In 1964, the International Union of Biochemistry recommended a systematic nomenclature for enzymes and classified them into six major types: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Each class of enzymes catalyzes different types of reactions, such as oxidation/reduction, group transfers, hydrolysis, isomerization, or bond formation.

1. Nomenclature and
classification of enzyme

2. ENZYMES:
 Enzymes are defined as biocatalysts, produced by the living cells
 which catalyse many biochemical reaction in animals and plant bodies.
 Enzymes help speed up the chemical reaction in the human body.
 They bind to molecules and after then in specific ways.
 They are essential for respiration , digesting food, muscle and nerve
function among thousands of other roles.

3. Nomenclature of Enzymes
 Enzymes are generally named according to the substrate it catalyses .
 Some enzymes were named before a systematic way of naming enzyme was formed.
 The pepsin , trypsin and chymotrypsin covey without information about the function of enzyme or the
nature of the substrate on which they act.
 The suffix - ase to the end of the name of the substrate enzymes named involved.
 Example of Urease which catalyse the breakdown of urea.
 Therefore, in 1964, a systematic nomenclature for enzyme was recommended by a commission
of International Union of Biochemistry.
 The IUB was discovered mainly six major classification of enzymes.

4. Classification of Enzymes
 OXIDOREDUCTASES:
 The enzymes that transfer H or O atoms, or electrons from one molecule to another, i.e.( catalyze involved oxidation and reduction
processes)
 The oxidoreductase is of two types: i) Dehydrogenase, that involves transfer of hydrogen.
 Dehydrogenase
AH2 + B ———————————————– A + BH2 – transfer of H2
Oxidase that involves of Oxygen.
 Reductases, which transfers electrons or electron to oxygen.
 Oxidase
 AH2 + O ———————————————– A + H2O

5. Transferases
 These are enzymes that catalyses transfer of a specific group from a
donor molecule to an acceptor molecule.
 The group may be methyl-, acyl-, amino-, or phosphate.
 such as trans-methylases , transaminases, phosphorylase etc.
 A-X + C ———————————————– A + B-X
 Transaminases, which transfer amino groups.

6. Hydrolases
 The enzymes catalyse the addition of water across a specific bond of the substrate to form the
products.
 A-B + H2O ———————————————– AH + BOH
 The Hydrolases include:
 Proteinase, that hydrolyse protein by breaking peptide bonds.
 Ribonucleases, which hydrolyse RNA.
 Deoxy-ribonucleases, responsible for hydrolysis of DNA.
 Lipases, which hydrolyses fats (esters).

7. Lyases
 These enzymes bring about non-hydrolytic addition or removal of groups from
substrates. During the reactions, C-C, C-N, C-O or C-S bonds may be split.
 A-B + X-Y ———————————————– AX- BY
 Decarboxylases, that removes CO2.
 Decarboxylase
 CH3COCOOH ——————– CH3CHO + CO2
 Carboxylases, that add CO2.
 RuBP carboxylase
 RUBP + H2O + CO2 ———————————————– 2GP

8. Isomerases
 Enzymes involved in all the isomerization reaction.
 Theses enzymes are responsible for intermolecular rearrangement.
 one isomer is converted to another.
 For example, during respiration glucose 1-phosphate is converted into
by phosphoglucomutase.
A---------------------------------------------A’
INTERCONVERTION OF ISOMERS

9. Ligases
 Ligases is the class of enzyme that brings about the binding or joining of two
molecules.
 The two macromolecules by forming new bonds like C-C, C-N, C-O or C-S

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