The accumulation of orotic acid by a pyrimidineless mutant of Neurospora

The discovery of orotic acid (1,2-carboxyuracil) in cow's milk by Biscaro and Belloni (1), followed by its identification and synthesis (2-4), led to a number of speculations as to its biological origin and significance (,3,5,6). A definite connection of orotic acid with the biosynthesis of nucleic acid pyrimidines is provided by the finding that orotic acid (7) as well as thymine (8,9) can supplement or replace the folic acid required by certain microorganisms. As suggested by Chattaway (7), it would appear that folic acid has a function in the biosynthesis of pyrimidines. Furthermore, this function is probably concerned in some step prior to the appearance of orotic acid in the biosynthetic series. More recently it was shown by Loring and Pierce (10) that orotic acid could be substituted for uracil in satisfying the growth requirements of some pyrimidineless mutants of the mold Neurospora. Investigations of orotic acid in this laboratory have led to a new method of synthesis of the compound (11) and to some suggestions concerning its relation to the biosynthesis of nucleic acids in Neurospora (12). The results of the present work are in accord with the previous suggestions and provide further evidence on the biological origin and function of orotic acid

The use of isotopic carbon in a study of the metabolism of anthanilic acid in Neurospora

The finding by Tatum, Banner, and Beadle (l), that the tryptophanless Neurospora mutant strain 10575 accumulates anthranilic acid, which in turn can be utilized for growth of strain 40008, has provided evidence that anthranilic acid is a biochemical precursor of tryptophan in this organism. It has been further established that indole is an intermediate in this conversion (2-5). More recent work with a number of mutants of Neurospora (6-8) has established that tryptophan is a biochemical precursor to niacin with kynurenine and hydroxyanthranilic acid as intermediates. The accumulated evidence has indicated the existence in the mold of the following series of reactions: → Anthranilic acid → indole → tryptophan → kynurenine → 3-hydroxyanthranilic acid → nicotinic acid In the light of this evidence the present work was undertaken to trace the carbon in the carboxyl group of anthranilic acid in order to estimate its contribution as a structural unit in the formation of niacin and tryptophan. The organism chosen for this investigation was a biochemical mutant strain of Neurospora designated as strain 40008. This mutant utilizes anthranilic acid, indole, or tryptophan for growth. The mutant was grown in the presence of anthranilic acid containing Cl4 in the carboxyl group. Niacin and tryptophan were isolated from the mold mycelium and tested for radioactivity

A Metabolic Relationship Between the Aromatic Amino Acids

The present work involves a further investigation of a Neurospora mutant, C-86, previously mentioned by Lein, Mitchell and Houlahan (1) as one that can utilize anthranilic acid, indole, tryptophan, kynurenine, 3-hydroxyanthranilic acid, and nicotinic acid as supplements for growth. Mutant C-86, when crossed to a “wild-type” strain, was found to differ from this wild type strain, with respect to tryptophan biosynthesis, by a mutation at a single locus. The evidence presented suggests the possibility of a common precursor to the aromatic amino acids

Hydroxyanthranilic Acid as a Precursor of Nicotinic Acid in Neurospora

Recent investigations in this laboratory(1) have provided evidence that the biosynthesis of nicotinic acid in Neurspora proceeds from tryptophane through the intermediate kynurenine I

Utilization By The Rat Of 3-Hydroxyanthranilic Acid As A Substitute For Nicotinamide

Experiments by a number of workers have established the fact that addition of tryptophan to the diet results in increased synthesis of nicotinic acid by a number of mammals

The use of isotopic nitrogen in a study of the conversion of 3-hydroxyanthranilic acid to nicotinic acid in Neurospora

Recent studies with mutant strains of Neurospora indicated that 3-hydroxyanthranilic acid (3-hydroxy-2-aminobenzoic acid) is an intermediate in the metabolic conversion of tryptophan to nicotinic acid. Evidence for this conversion in mammals is found in the report that 3-hydroxyanthranilic acid can maintain the growth of rats on a nicotinic acid-deficient diet and in the work of Albert, Scheer, and Deuel, who found an increased excretion of N-methylnicotinamide by rats fed this substance. The isotopic experiments of Heidelberger, Abraham, and Lepkovsky demonstrated that the carboxyl carbon of 3-hydroxyanthranilic acid is the precursor of the carboxyl carbon atom of nicotinic acid. To study the mechanism of the conversion of the benzene ring into a pyridine derivative, a mutant strain of Neurospora crassa C-86, requiring 3-hydroxyanthranilic acid or a precursor for growth, was grown in a medium which contained non-labeled synthetic 3-hydroxyanthranilic acid and Nls ammonium chloride as the only sources of nitrogen. Thus the absence of N16 in excess in nicotinic acid isolated from the mold would indicate that the amino group of 3-hydroxyanthranilic acid is the precursor of the pyridine nitrogen in nicotinic acid