Question

The covalent catalytic mechanism of an enzyme depends on a single active site Cys whose pK is 8. A mutation in a nearby residue alters the microenvironment so that this pK increases to 10. Would the mutation cause the reaction rate to increase or decrease? Explain.

Answer 1

Answer: The reaction rate will INCREASE

Explanation: enzymes are not consumed by the reaction they catalyse, enzyme assay usually follow changes in the concentration of substrate or product to measure the rate of reaction. Now the cys active site contains thiolate ion which will increase on increase of the pk from 8 to 10. Hence increasing the rate of reaction which is catalysed by the active form of the enzyme.