Tryptophan 3-hydroxyanthranilic oxidase

Figure 8.4. Pathways of tryptophan metaholism. Tryptophan dioxygenase, EC 1.13.11.11 formylkynurenine formamidase, EC 3.5.1.9 kynurenine hydroxylase, EC 1.14.13.9 kynureninase, EC 3.7.1.3 3-hydroxyanthranilate oxidase, EC 1.10.3.5 picolinate carboxylase, EC 4.1.1.45 kynurenine oxoglutarate aminotransferase, EC 2.6.1.7 kynurenine glyoxylate aminotransferase, 2.6.1.63 tryptophan hydroxylase, EC 1.14.16.4 and 5-hydroxytryptophan decarboxylase, EC 4.1.1.26. Relative molecular masses (Mr) tryptophan, 204.2 serotonin, 176.2 kynurenine, 208.2 3-hydroxykynurenine, 223.2 kynurenic acid, 189.2 xanthurenic acid, 205.2 and quinolinic acid 167.1. CoA, coenzyme A.

In independent studies, Aprison et al. (A7) found among tryptophan metabolites that 3-hydroxyanthranilic acid was capable of inhibiting the oxidation of N,N-dimethyl-p-phenylendiamine by purified ceruloplasmin and serum oxidase. 

Figure 2 NAD metabolism. Tip = tryptophan, 3-HK = 3-hydroxykynurenine, 3-HA = 3-hydroxyanthranilic acid, ACMS = a-amino-P-carboxymuconate- -semialdehyde, AMS = a-aminomuconate- -semialdehyde, NaMN = nicotinic acid mononucleotide, NMN = nicotinamide mononucleotide, NaAD = nicotinic acid adenine dinucleotide. For other abbreviations, see Figure 1. (1) tryptophan oxygenase [EC 1.13.11.11], (2) formy-dase [EC 3.5.1.9], (3) kynurenine 3-hydroxylase [EC 1.14.13.9], (4) kynureninase [EC 3.7.1.3], (5) 3-hydroxyanthranilic acid oxygenase [EC 1.13.11.6], (6) nonenzymatic, (7) aminocarboxymuconate-semialdehyde decarboxylase [EC 4.1.1.45], (8) quinolinate phos-phoribosyltransferase [EC 2.4.2.19], (9) NaMN adenylyltransferase [EC 2.7.2.18], (10) NAD synthetase [EC 6.3.5.1], (11) NAD kinase [EC 2.7.1.23], (12) NAD" glycohydro-lase [EC 3.2.2.5], (13) nicotinamide methyltransferase [EC 2.2.1.1], (14) 2-Py-forming MNA oxidase [EC 1.2.3.1], (15) 4-Py-forming MNA oxidase [EC number not given], (16) nicotinamide phosphoribosyltransferase [EC 2.4.2.12], (17) NMN adenylytransferase [EC 2.7.71], (18) nicotinate phosphoribosyltransferase [EC 2.4.2.11], (19) nicotinate methyltransferase [EC 2.7.1.7], and nicotinamidase [EC 3.5.1.19]. Solid line, biosynthesis dotted line, catabolism.

Several alternative pathways of L-tryptophan metabolism diverge from kynurenine (24). In mammals the quantitatively major fate of the benzene ring of the amino acid appears to be its oxidation to carbon dioxide via 3-hydroxyanthranilic acid (25), Figure 4.5. Kynurenine is first hydroxylated by a typical mixed function oxidase and the side chain is then removed, under the... 

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