Question

How do we measure the concentration of the enzyme?

(a) In units of mass

(b) In units of time

(c) In units of activity

(d) In units of volume

This question was posed to me in an interview for internship.

This interesting question is from Basic Reaction Theory in section Homogenous Reactions of Bioprocess Engineering

Answer 1

The correct option is (c) In units of activity

To elaborate: The mass of a particular enzyme added to a reaction is rarely known; most commercial enzyme preparations contain several components in unknown and variable proportions depending on the batch obtained from the manufacturer. To overcome these difficulties, enzyme quantity is often expressed as units of activity measured under specified conditions. One unit of enzyme is usually taken as the amount which catalyses conversion of 1μmol substrate per minute at the optimal temperature, pH and substrate concentration.