Multienzyme complex

Multienzyme complex contains several copies of one or several enzymes (polypeptide chains) packed into one assembly. Multienzyme complex carries out a single or a series of biochemical reactions taking place in the cells. It allows to segregate certain biochemical pathways into one place in the cell.

Examples include pyruvate dehydrogenase, fatty acid synthetase, glutamine synthetase, proteasome, rubisco.

A multienzyme complex that functions in the histidine biosynthesis pathway has been studied at the biochemical and genetic level in the fungus Neurospora crassa. A gene (His-3) was found to encode a protein that functions as a multienzyme complex having three distinct enzymatic activities in the biosynthesis pathway. A genetic analysis of mutants defective in the N. crassa histidine pathway indicated that the individual activities of the multienzyme complex occur in discrete regions of the His-3 genetic map. This finding suggested that each of the activities of the multienzyme complex are encoded separately from each other, but within the same gene. Some His-3 mutants were also found that lacked all three activities simultaneously, suggesting that some mutations can cause loss of function of the whole multienzyme complex.