Enzyme Kinetics - Introduction

Introduction to Enzyme Kinetics

Most of the chemical reactions which occur in living systems, if left to their own devices, would occur at rates which are very slow, some immeasureably slow. Catalysts are required to make these reactions go at rates that are useful to the cell. In biological systems the catalysts are enzymes.

What are catalysts? And what do they do? In order to understand this lets first look at a simple chemical reaction of the type:

If the reaction is allowed to proceed without interference, it eventually appears to stop. What really has happened is that the forward and reverse reactions are going on at the same rate. This state is called equilibrium and can be described by the equilibrium constant:

This constant is characteristic of the reaction and can be approached from either direction. A catalyst increases the rate at which the reaction approaches equilibrium, but it does not alter the nature of the state of equilibrium, e.g. the concentration of the reactants at equilibrium. One other important property of catalysts is that they are effective in very small amounts, referred to as catalytic amounts. Stoichiometric amounts are not needed.

If we are to understand how enzymes do their job we must study enzyme kinetics, the study of rates. Some questions are:

What affects rates?
How are rates determined?
How are kinetic parameters determined?

Let's find out!