Hydroxyanthranilic acid conjugated

Also Tojo and Uenoyama (T2) by means of paper chromatography detected neither 5-hydroxyanthranilic acid nor its conjugate forms in urine of senile cataract patients. They found, however, an ethanol-extractable substance giving a positive ninhydrin reaction and Rf value coinciding with that of tryptophan. The oral administration of a dose of anthra-nilic acid did not alter their findings. 

Both anthranilic acid and hydroxyanthranilic acid can be formed from tryptophan in insect mutants, and both are conjugated with glycine to give substituted hippuric acids (796), whereas in plants or bacteria anthranilic acid tends to be conjugated as the /3-glucoside (848). 

Nicotinic Add Metabolism. The sequence of reactions leading to the formation of pyridine compounds is of particular interest as a source of nicotinic acid. Nutritional, isotopic, and genetic experiments have all shown that tryptophan and its metabolic derivatives including 3-hydroxy-anthranilic acid are precursors of nicotinic acid in animals and in Neuro-spora. The terminal steps in this sequence are not known. Under certain physiological conditions an increase in picolinic carboxylase appears to reduce nicotinic acid synthesis. This implies a common pathway as far as the oxidation of 3-hydroxyanthranilic acid. Whether quinolinic acid is a precursor of nicotinic acid is still uncertain. The enzyme that forms the amide of nicotinic acid also has not been isolated. Subsequent reactions of nicotinamide include the formation of the riboside with nucleoside phosphorylase and methylation by nicotinamide methyl-kinase. In animals W-methylnicotinamide is oxidized to the corresponding 6-pyridone by a liver flavoprotein. Nicotinic acid also forms glycine and ornithine conjugates. Both aerobic and anaerobic bacteria have been found to oxidize nicotinic acid in the 6-position. ... 

Mehler (69) has found that compound I can be decarboxylated to yield picolinic acid [reactions (Ilb) and (Illb), Fig. 2]. The formation of this pyridine derivative appears to take place in two steps with the formation of an open chain unsaturated aldehyde as an intermediate. Mehler s enzyme is specific with respect to the formation of picolinic acid and does not promote the conversion of compound I to nicotinic acid and does not decarboxylate quinolinic acid. Picolinic acid is not present in urine in large amounts following 3-hydroxyanthranilate injection (28). However, the glycine conjugate, picolinuric acid, appears to be excreted when the anthranilic acid is administered (70). 

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