The mechanism of death of yeast cells due to biotin deficiency in the presence of aspartic acid (Asp medium) was further studied. Total fatty acids of yeast cells per culture or per dry cell weight grown in biotin-sufficient Asp medium increased with time, but they did not increase in biotin-deficient condition, although the growth was observed. Each of fatty acids such as palmitic, palmitoleic, stearic, and oleic acids, which are main component of yeast cells, scarcely increased for 8hr in biotin-deficient Asp medium, although they increased gradually in biotin-sufficient condition. The effect of various fatty acids on cells grown under biotin-free Asp medium was examined and a supplementation of palmitoleic, oleic, or linolenic acid promoted the cell growth, same as that of biotin, and saved the yeast from death completely. It was confirmed by using oleic acid-requiring mutant of
Saccharomyces cerevisiae that cell death also occurred by oleic acid deficiency even in the biotin-sufficient condition.
From these results, a primary cause of death due to biotin deficiency was assumed to be the insufficient synthesis of the main component of cell fatty acids such as palmitic, palmitoleic, stearic, and oleic acids during the growth of cells induced by the addition of aspartate.
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