Question

Substrate of an enzyme is

• A. the reactant of the reaction catalysed by the enzyme
• B. competitive inhibitor of the enzyme
• C. uncompetitive inhibitor of the enzyme
• D. prosthetic group of the enzyme

Answer 1

The correct option is A the reactant of the reaction catalysed by the enzyme

Enzymes are also called biocatalysts, which speed up a particular reaction without getting altered. They have specific sites on them, also called active sites, on which the reactants bind to. This reactant is also referred to as substrate of the enzyme. The enzymes and substrate form enzyme-substrate complex. This then gets transformed into enzyme-product complex after the reaction. Finally, the products are released from the respective enzymes, the latter get ready for subsequent rounds of reactions.

$\begin{array}{ccccccccccc}\text{E}& +& \text{S}& \rightleftharpoons & \text{ES}& \rightleftharpoons & \text{EP}& \rightleftharpoons & \text{E}& \text{+}& \text{P}\\ \text{Enzyme}& & \text{Substrate}& & \text{Enzyme}& & \text{Enzyme}& & \text{Enzyme}& & \text{Product}\\ & & & & \text{Substrate}& & \text{Product}& & & & \\ & & & & \text{complex}& & \text{complex}& & & & \end{array}$

Inhibitors tend to decrease the activity of the enzymes, either by competing with substrates to fit into active site or by binding to sites other than active sites or ES complex which hamper the progress of reaction.

Prosthetic groups are the non-protein part of conjugate enzymes which tightly bind to the protein part (apoprotein) to confer functionality to the enzymes.