Studies on yeast metabolism. 6. Effects of thiamine on nitrogen assimilation during fermentation, and on fermentation kinetics

Abstract

Acceleration of the fermentation rate of baker''s yeast by thiamine depends on synthesis of fermentation enzymes from nitrogenous constituents of the medium. This synthesis occurs in phosphate-free medium, but its effect on rate is masked by the dilution of intracellular phosphorylated substrates due to cell division. This synthesis is restricted in the absence of thiamine. Cell division, nucleic acid and overall protein synthesis are less affected. High intracellular level of pyruvate and alanine may interfere with protein synthesis. Carboxylase synthesis during fermentation occurs only in the presence of thiamine, but the low intracellular pyruvate level shows that carboxylase is not a limiting enzyme in fermentation by thiamine-saturated yeast. Fermentation-rate control appears to be a complex process involving factors other than the level of fermentation enzymes.