Regulation of Folate Metabolizing Enzymes In Fungus Aspergillus nidulans

Abstract

The regulation of methionine synthase. serine hydroxymethyltransferase. methylenetetrahydrofolate oxidorelluctase and dihydrofolate reductase in Aspergillus nidulans have been found to be controlled by endogenous pools methionine and homocysteine. Mutants impaired in sulfur metaholite repression. which have highly elevated pools of these amino acids. also show elevated levels of folate metabolizing enzymes mentioned above. This effect was found to he the result of the accumulation of endogenous homocysteine. which induces folate enzymes. High concentration (up to 5 mM) or methionine in growth medium leads to repression of these enzymes. It appears. therefore. that the levels of folate metaholizing enzymes arc determined by the ratio of cellular levels or methionine and homocysteine.

Keywords

• methionine synthase
• serine hydroxymethyltransferase
• dihydroiolate reductase
• methylenetetrahydrofolate oxidoreductase
• aspergillus