EFFECT OF AERATION ON THE SYNTHESIS OF NICOTINIC ACID AND NICOTINAMIDE ADENINE DINUCLEOTIDE BY BAKER'S YEAST

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Abstract
Anaerobiosis limited the ability of baker's yeast to synthesize nicotinic acid, whether the test organism was an anaerobically precultured yeast, or an aerobically produced commercial baker's yeast. The effect appeared both in the total amounts of nicotinic acid and NAD-NADH2,* 1 NAD-NADH2 = Oxidized and reduced forms of nicotinamide adenine dinucleotide. and also in the growth of the yeast. Hence, nicotinic acid must be considered a necessary growth factor for baker's yeast under anaerobic conditions. The mechanism of nicotinic acid synthesis was investigated by studying the growth-stimulating properties of the different intermediates. Synthesis by baker's yeast does not proceed in the way reported for Escheriehia coli, and compounds derived from aspartic acid and ornithine did not promote the synthesis of nicotinic acid by yeast. On the other hand some of the compounds of the tryptophan series, 3-hydroxykynurenine, 3-hydroxyanthranilic acid and quinolinic acid, were found to promote synthesis under anaerobic conditions. Oxidation of kynurenine to 3-hydroxykynurenine is considered to be the limiting step in the synthesis of nicotinic acid by baker's yeast under anaerobic conditions. 3-Hydroxyanthranilic acid increased the content of nicotinic acid in baker's yeast under aerobic conditions also.