Biochemistry in Tables, Schemes, and Graphs - S.D. Zhamsaranova 2009

Enzymes
Classification of Enzymes

Enzymes (E) are protein catalysts that accelerate cellular reactions.

Similarities between enzymes and chemical catalysts:

- they increase reaction rates without being consumed in the process or undergoing irreversible changes;

- they do not alter The equilibrium state of a chemical reaction, accelerating both the forward and reverse reactions to the same extent;

- they increase reaction rates by lowering the activation energy, which is the energy barrier separating one state of the system from another.

Differences between enzymes and non-biological catalysts:

- high catalytic efficiency;

- high catalytic Specificity — The ability to select a specific substrate and catalyze a particular reaction;

- mild conditions for enzymatic reactions: Temperature of 370С, normal atmospheric pressure, and a near-neutral pH;

- susceptibility to regulation.

Class

Type of catalyzed reaction

Oxidoreductases

Oxidation-reduction reactions

Transferases

Transfer of specific groups of atoms from a donor molecule to an acceptor molecule

Hydrolases

Hydrolytic Cleavage of bonds (involving Water)

Lyases

Cleavage of bonds by means other than Hydrolysis or oxidation

Isomerases

Interconversion of various isomers

Ligases (synthetases)

Formation of bonds via the Condensation of two different compounds (utilizing ATP energy)

SOME METAL-DEPENDENT ENZYMES

Enzyme

Metal ion

Metal ion function

Hexokinase

Mg2+

Substrate binding

Pyruvate kinase

Mg2+, К+

Substrate binding and catalysis

Pyruvate carboxylase

4Mn2+

Catalysis

а-Amylase

Са2+ (Cl-)

Stabilization of tertiary Structure

Transketolase

Са2+

Stabilization of quaternary


structure

Superoxide dismutase

2Zn2+,2Cu2+

Catalysis

Carboxypeptidase A

Zn2+

Catalysis

Arginase

4Mn2+

Substrate binding and catalysis





Last update: 06/08/2026

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