The effect of myo-inositol on pyruvate decarboxylase.

Abstract

Saccharomyces carlsbergensis 4228 (ATCC 9080) was cultivated for 24 hours in four different media containing 0, 50, 150 and 500μg of myo-inositol per 20ml. The growth of the yeast and the specific activity of pyruvate decarboxylase extracted from the respective cell preparations were found to be proportional to the amount of inositol in the medium. The level of acetoin in the culture medium decreased reversely with the concentration of inositol. Both acetoin accumulation and Pyruvate decarboxylase activity of the yeast were influenced significantly by the lots of Casamino acid used as a nitrogen source in the basal medium. Among five Casamino acid peparations tested, R 69 and NR 1219 gave the highest and the lowest “acetoin ratio” respectively. With the amino acid mixtures reconstituted on the basis of amino acid analysis of the two Casamino acids, the patterns of acetoin accumulation were the same as those obtained with respective Casa-mino acid. The increasing responses of pyruvate decarboxylase to the concentration of inositol in the medium observed with Casamino acid, however, were not reproduced with the reconstituted amino acid mixtures. Variation of the acetoin level in the culture medium seems to be caused by the composition of amino acids in the lots and the activation of pyruvate decarboxylase by inositol seems to be ascribed to an unknown substance in Casamino acid.