Hankes Lv, Henderson Lm
Mar 1, 1957
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Journal
Journal of Biological Chemistry
Abstract
Since 3-hydroxyanthranilic acid was established as an intermediate in the biosynthesis of nicotinic acid in Neurospora crassa (1, 2), its role in animals (3-5) and surviving tissues (6, 7) has been studied. It is known that 3-hydroxyanthranilate may rise from 3-hydroxykynurenine by the catalytic action of kynureninase (8). Approximately 10 per cent (9) of a test dose of 3-hydroxyanthranilic acid is excreted as urinary quinolinic acid. The conversion of 3-hydroxyanthranilate to pyridine nucleotides was established by its niacin-replacing activity in rats receiving niacinfree, tryptophan-low diets (3-5). Further evidence for the role of 3-hydroxyanthranilic acid as a precursor of niacin was provided by the demonstration that rats excreted increased amounts of N'-methylnicotinamide when 3-hydroxyanthranilic acid was administered (10). Proof of this relationship was provided by injecting C' 4-carboxyl-labeled 3-hydroxyanthranilic acid and isolating labeled N'-methylnicotinamide from the urine (11). The studies reported here show that the carboxyl group of 3-hydroxyanthranilic acid is rapidly disposed of as CO2 when this compound is injected into normal rats receiving a 9 per cent casein diet. Essentially all of the C'4 in the quinolinate excreted following injection of carboxyl-labeled 3-hydroxyanthranilic acid was present in the 3-carboxyl carbon.