The Identification of a Natural Precursor of Nicotinic Acid

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Abstract
A strain of Neurospora (#4540) requiring either nicotinic acid or nicotinamide, grown in limiting amounts of either compound, produces a substance which shows nicotinic acid activity for another mutant genetic type of Neurospora (#39401). Fractionation of the culture filtrate (of #4540) gives a crystalline compound as active as nicotinic acid for growth of #39401. This compound''s empirical formula is C7H7O3N. The mol. wt. suggests a C6 or C7 structure. Physical properties, including absorption spectra curve and biol. activity, are identical with 3-hydroxyanthranilic acid (2-amino 3-hydroxy benzoic acid). Biosynthesis of nicotinic acid in Neurospora therefore may be: [forward arrow] anthranilic acid [forward arrow] indole [forward arrow] trypto-phane [forward arrow] kynurenine [forward arrow] 3-hydroxyanthranilic acid [forward arrow] nicotinic acid. This scheme contains discrepancies and does not explain activities shown by some genetic strains of Neurospora and rats.