Understanding Enzyme Kinetics: Calculating KM and Vmax

The kinetics of a bacterial dehalogenase were investigated.

The study aimed to understand the enzyme kinetics of a bacterial dehalogenase. Enzymes are biological catalysts that speed up chemical reactions in living organisms. Dehalogenases, in particular, are enzymes that can remove halogen atoms from organic compounds.

Calculate KM and Vmax from the following data:

[S] (mM) ν0 (nmol·min^-1)

0.04 0.229

0.13 0.493

0.40 0.755

0.90 0.880

1.30 0.917

What is the KM (mM)?

Final answer: In this situation, the KM or Michaelis-Menten constant describes the substrate concentration ([S]) at which the reaction velocity is half the maximal rate (Vmax). Using the data provided, Vmax seems to be about 0.917 nmol·min^-1. Therefore, KM will be the substrate concentration when the rate is half of that, which according to the data, is approximately around 0.13 mM.

Explanation:

The KM or Michaelis-Menten constant of an enzyme is a characteristic of enzyme activity. Here, we're dealing with an enzyme called a dehalogenase. KM indicates the substrate concentration ([S]) at which the reaction velocity (ν0) is half of Vmax. The Vmax represents the maximum rate achieved by the enzyme. Based on the provided data, the maximum velocity (Vmax) appears to be approaching 0.917 nmol·min^-1 (the rate at highest [S]), so KM will be the concentration at which the velocity is around half of this (0.917/2 = 0.4585 nmol·min^-1). Looking at your data, this occurs approximately around 0.13 mM.

KM plays a crucial role in enzyme kinetics as it helps determine the affinity of an enzyme for its substrate. A lower KM value indicates a higher affinity, meaning the enzyme can effectively bind to the substrate even at low concentrations. On the other hand, a higher KM value suggests lower affinity, requiring higher substrate concentrations for efficient enzyme-substrate interaction. Understanding KM is essential for optimizing enzyme reactions in various biological processes.