SUMMARY: Growth of a strain of in a glucose salts vitamins medium, containing suboptimal concentrations of biotin, was accompanied by the appearance in the medium of a free form of nicotinic acid, and also a heat-labile combined form of this substance; these were identified chromatographically as nicotinic acid and desamido-DPN (nicotinic acid adenine dinucleotide), respectively. The effect of biotin concentration and incubation time on the excretion of these substances is reported. The presence of adenine in the growth medium caused a marked decrease in the excretion of both forms of nicotinic acid, but hypoxanthine and 4-amino-5-imidazole carboxamide had no observable effect. Addition of dl-aspartic acid to the medium also brought about a decrease in the amounts excreted, although concentrations of this amino acid in excess of 0·5 x 10m stimulated excretion of desamido-DPN. It is concluded that excretion of free nicotinic and desamido-DPN is largely the result of an impairment in the ability of the biotin-deficient yeast to produce adenine, which in turn leads to a derangement in the synthesis of pyridine nucleotides.


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