RESTING CELL STUDIES ON FORMATION OF WATER-SOLUBLE RED PIGMENTS BY MONASCUS SP

A resting cell system was developed for the biosynthesis of soluble re d pigments by Monascus. The medium contains glucose, glycine, ZnSO4 an d MnSO4 in pH 7.0 MOPS buffer containing cycloheximide to prevent prot ein synthesis. The linear production observed over a period of at leas t four h was due to de novo polyketide synthesis and biological methyl ation, as shown by inhibition with cerulenin, iodoacetamide and ethion ine. Production was inhibited by carbonyl reagents and stimulated by p yridoxamine suggesting that the conversion of endogenous intracellular orange pigments to extracellular red pigments involves Schiff base in termediates and vitamin B6 a cofactor. The resting cell system was use d to study the mode of action of nutritional effectors previously pinp ointed by experiments with growing cells. The negative effects of high concentrations of phosphate and Mg++ are due to inhibition of pigment synthase action, not to repression or inactivation of these enzymes. The positive effects of trace metals, especially Zn++, are due to stim ulation of growth and enzyme action, not to induction or stabilization of the synthases.