[Effects of enzyme inhibitors on the pigment synthesis in Monascus anka]

Monascus pigment is a natural, safe pigment and preservative. Six inhibitors of key enzymes from three metabolic pathways were chosen according to databases, and were used in basic medium to study their effects on the pigment synthesis in Monascus anka strain M5034. Trimethylamine, inhibitor of shikimic acid pathways, and anthranilic acid and 3,4-dihydroxybenzoic acid, inhibitors of mevalonic acid pathways, had no effects on the pigment biosynthesis. Pigment biosynthesis was severely inhibited by three inhibitors of the key enzymes in the polyketide pathways at the concentrations with no effects for growth of the strain. lodiacetamide (lower than 0.5 mmol/L), specific inhibitor of beta-ketoacyl-acylcarrier protein (ACP) synthase, reduced remarkably the pigment synthesis by 64.7%; 1.0 mmol/L imidazole, being nonspecific inhibitor of ACP synthase, could strongly suppress the synthesis of pigment by 60%, and 0.5 mmol/L 2,4-dinitrofluorobenzene, inhibiting the activity of thioesterase, strongly limited the pigment production with inhibitory extent up to 91.5%. All data implied that Monascus pigments might be synthesized through polyketide pathway.