Question

18. KM is—

A) an indicator of how strongly an enzyme binds its substrate.

B) the rate at which the enzyme binds the substrate.

C) the rate constant for the reaction ES ® E + P.

D) a measure of enzyme efficiency.

E) a measure of substrate turnover.

Answer 1

Ans18(A) Km is an indicator of how strongly an enzyme binds its substrate.

- Km represents the substrate concentration at which half the enzyme sites are filled by substrate molecules. It is equal to the substrate concentration at half the maximum rate.

- The greater value of Km indicates the less affinity of substrate or the less tightly the substrate is bound to the enzyme & the lower value of Km describes the greater affinity of enzymes for the substrate.  Km is therefore used as a measure of how tightly the substrate is bound to the enzyme.

- Km depends upon the temperature, nature of substrate, pH, ionic strength & other reaction conditions, therefore its value serves to characterize a particular enzyme- substrate system under specific conditions.

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