Isozymes, (or isoenzymes) are isoforms (closely related variants) of enzymes. In many cases, they are coded for by homologous genes that have diverged over time.
In some instances, different variants of some enzymes have developed different regulatory properties, which can improve the range, rapidity, or flexibility of response to a changing metabolic environment. The different isozymes can, for example, have different Km values or be inhibited/activated by different effectors.
An example of an isozyme is glucokinase, a variant of hexokinase which is not inhibited by glucose 6-phosphate. Its different regulatory features and lower affinity for glucose (compared to other hexokinases), allows it to serve different functions in cells of specific organs, such as control of insulin release by the beta cells of the pancreas, or initiation of glycogen synthesis by liver cells. Both of these processes must only occur when glucose is abundant, or problems occur.
Isozymes (also known as isoenzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction.
An example of an isozyme is glucokinase, a variant of hexokinase which is not inhibited by glucose 6-phosphate.
To identify isozymes, a crude protein extract is made by grinding animal or plant tissue with an extraction buffer, and the components of extract are separated according to their charge by gel electrophoresis.
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