The role of myo-inositol in metabolic control. The effect of myo-inositol on pyruvate decarboxylation in Saccharomyces carlsbergensis

The effect of myo-inositol deficiency on phosphatases of yeast

Activities of several phosphohydrolases are significantly enhanced when cells of the inositol-requiring yeast, Saccharomyces uvarum ATCC 9080, are deprived of inositol. This effect is most pronounced for the external acid phosphatase and cannot be explained simply by limitation of cellular growth, because starvation for vitamins or sulphate has no effect on acid phosphatase activities. Excessive secretion of acid phosphatase by spheroplasts prepared from inositol-deficient cells is greatly reduced when the spheroplast medium is supplemented with inositol and is immediately suppressed by the addition of cycloheximide. These results together with data obtained from experiments with whole cells, employing cycloheximide and actinomycin D, point to a regulatory effect of inositol limitation at the level of transcription. The external enzymes beta-D-fructofuranosidase, alpha-D-galactosidase and L-asparaginase, and the vacuolar enzyme carboxypeptidase Y are not affected by inositol deficiency indicating that inositol deficiency has no general effect on protein secretion.

Lipid metabolism in inositol-deficient yeast, Saccharomyces carlsbergensis. The influence of temperature and anaerobiosis on the cellular lipid composition

Saccharomyces carlsbergensis ATCC 9080 was grown at temperatures of 9, 25, 30 and 35 degrees C, respectively. At all temperatures inositol-deficient cells contain less phosphatidylinositol than supplemented cells. Total acylglycerols increase in supplemented cells as the temperature decreases whereas in deficient cells total acylglycerols are higher at 35 degrees C than at 9 degrees C. Temperature has little influence on the fatty acid composition of the supplemented as well as on that of the deficient cells. Under anaerobic growth conditions two major effects of inositol deficiency observed under aerobic conditions, i.e. accumulation of cellular triacylglycerols and increased production of acetoin, do not occur. Other effects of inositol deficiency, such as increased glucose utilization, increase of ethanol production, decrease of phosphatidylinositol and aggregation of cells, are observed under anaerobic conditions as well as under aerobic conditions.