3- Hydroxyanthranilate, metabolite

Figure 30-16. Formation of xanthurenate in vitamin Bg deficienqr. Conversion of the tryptophan metabolite 3-hydroxykynurenine to 3-hydroxyanthranilate is impaired (see Figure 30-15). A large portion is therefore converted to xanthurenate.

The analysis of amino acids involves chromatographic issues similar to those encountered in analysis of simple amines. Underivatized amino acids have, with a few exceptions, weak UV absorbance and a strong tendency to interact with stationary phases in undesirable ways. Underivatized amino acids are normally separated with ion exchange chromatography, then visualized post-column by reaction with ninhydrin, o-phthaladehyde (OPA), or other agents. Underivatized tryptophan and the metabolites kynurenine, 3-hydroxykynurenine, kynurenic acid, and 3-hydroxyanthranilic acid, were separated on a Partisphere 5-p ODS column with fluorescent detection.121... 

Reported redox potentials of laccases are lower than those of non-phenolic compounds, and therefore these enzymes cannot oxidize such substances [7]. However, it has been shown that in the presence of small molecules capable to act as electron transfer mediators, laccases are also able to oxidize non-phenolic structures [68, 69]. As part of their metabolism, WRF can produce several metabolites that play this role of laccase mediators. They include compounds such as /V-hvdi oxvacetan i I ide (NHA), /V-(4-cyanophenyl)acetohydroxamic acid (NCPA), 3-hydroxyanthranilate, syringaldehyde, 2,2 -azino-bis(3-ethylben-zothiazoline-6-sulfonic acid) (ABTS), 2,6-dimethoxyphenol (DMP), violuric acid, 1-hydroxybenzotriazole (HBT), 2,2,6,6-tetramethylpipperidin-iV-oxide radical and acetovanillone, and by expanding the range of compounds that can be oxidized, their presence enhances the degradation of pollutants [3]. 

It was furthermore reported (K20) that nicotinic acid-deficient animals would grow only if given tryptophan, thus suggesting the conversion of tryptophan to nicotinic acid. Not only is tryptophan converted to nicotinic acid but also kynurenine and 3-hydroxyanthranilic acid. The peculiar degradation of the latter to pyridine derivatives gave rise to many interesting investigations. 3-Hydroxyanthranilic acid is derived from 3-hydroxykynurenine, another important tryptophan metabolite, the his-... 

In the same year paper chromatography was first attempted by Benassi (B4) for the simultaneous analysis of 8 tryptophan metabolites (kyn-urenine, 3-hydroxykynurenine, kynurenic acid, xanthurenic acid, anthra-nilic acid, 3-hydroxyanthranilic acid, 2-aminoacetophenone, and 2-amino-3-hydroxyacetophenone), separated by means of a mixtiue of methanol, n-butanol, benzene, and water and revealed through the fluorescence in ultraviolet light of 3655 A. Each compound elicits a different fluorescent color (cf. Table 1). 

Fic. 3. Chromatographic fractionation of a mixture of tryptophan metabolites on an ion-exchange column of Amberlite IR-120 ( 28 X 0.9 cm). The temperature was held at 37 °C and the flow rate was adjusted at 12 ml per hour with formic acid-pyridine buffers. The metabolite concentration is given as (ig/ml after fluorometric readings. Effluent was collected in 2-ml fractions. The following abbreviations are used KA, kynurenic acid XA, xanthurenic acid AHA, o-aminohippuric acid K, kynurenine 30HAA, 3-hydroxyanthranilic acid 30HK, 3-hydroxykynurenine. 

As previously mentioned, 3-hydroxyanthranilic acid was found chro-matographically by Musajo et al. (M18) in the urine of tuberculous patients. This was the starting point for an extensive investigation of tryptophan metabolites excreted spontaneously, i.e., by normal subjects or patients with different diseases all fed a normal diet without added tryptophan. 

Excretion of 3-hydroxykynurenine and 3-hydroxyanthranilic acid is found to be increased in some of the patients with Hodgkin s disease (8 of 28), especially when the general conditions of the patients deteriorate. The other metabolites are present in normal quantities. 

Bladder and Kidney Cancer and Other Urological Diseases. The excretory pattern in cases of bladder tumor has been studied for many years in our laboratory (B5, B8) after Boyland and Williams (B18) had suspected that o-aminophenolic metabolites of tryptophan (i.e., 3-hydroxykynurenine, 3-hydroxyanthranilic acid, and 2-amino-3-hydroxy-acetophenone) might be endogenous agents of bladder cancer simi-... 

Of these only 60 excreted abnormal levels of urinary metabolites high amounts of 3-hydroxykynurenine and 3-hydroxyanthranilic acid were observed, respectively, in 29 and in 4 cases. However, the compound whose... 

From our investigation it is evident that abnormal excretion of tryptophan metabolites is not a typical feature of bladder tumor subjects, since human beings with neoplastic and nonneoplastic extrabladder urinary diseases have also been found to excrete spontaneously elevated amounts of tryptophan derivatives. It seems that the metabolic abnormality is not restricted to bladder tumors, but is rather more specific for patients with tumors of the upper urinary tracts and of the renal parenchyma. Actually 59% of these patients (Fig. 4) excreted abnormal amounts of kynurenine, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid. 

Quagliariello et al. (Ql) followed qualitatively (by means of onedimensional paper chromatography) the spontaneous excretion of kynurenines and anthranilic acids in 47 bladder tumor patients. They found that 3-hydroxyanthranilic acid was usually excreted and other metabolites only occasionally. Furthermore, Quagliariello (Q4) in an interesting review, reports that in urine of 15 bladder tumor patients 3-hydroxyanthranilic acid is excreted in amounts that are usually accepted as normal, whereas normal controls do not excrete 3-hydroxyanthranilic acid at all. 

It was recently observed (K2) that a kidney with a small tumor excretes more of the so-called carcinogenic o-aminophenols (3-hydroxykynurenine and 3-hydroxyanthranilic acid) than the opposite healthy kidney after a 100 mg/kg loading dose of L-tryptophan. The small size of the hypernephroma encountered at nephrectomy and also the higher excretion of carcinogenic metabolites of tryptophan previously thought to be restricted to tumors of transitional-cell epithelium (K2) are emphasized. 

Chronic schizophrenics excrete, on an average, 2.4 times the total amount of the metabolites excreted hy normal subjects. The ratio is different for each metabolite it is highest for 3-hydroxykynurenine, which is excreted in very small amounts by healthy people and in amounts about 9 times as large by schizophrenic subjects. It is lowest for 3-hydroxyanthranilic acid, the mean excretion of which slightly decreases in pathological conditions. Moreover, the schizophrenic patients excrete more kynurenic and xanthurenic acids than the healthy controls. 

These patients appear to excrete a slightly higher amount (8.9-12.3%) of tryptophan derivatives than normals (average 6.7%), The excretion ratios are different for each metabolite the highest ratio is found for 3-hydroxykynurenine and the lowest for 3-hydroxyanthranilic acid. 

Paper chromatographic analysis indicated that the abnormal excretion of xanthurenic acid always corresponded with higher amounts of other tryptophan metabolites such as kynurenine, acetylkynurenine, 3-hydroxy-kynurenine, and kynurenic and 3-hydroxyanthranilic acids after the usual load of tryptophan. 

Chizhova and Ivanova (C7) studied 20 children, aged 1-12 years, under therapy for leukemia and 10 healthy children as control. A total of 15-20 g of tryptophan was administered during 5-10 days (1.5-3 g/day) to 7 children whereas 13 were given a single dose of 2-3 g. Daily determinations of urinary metabolites by paper chromatography demonstrated a disturbance of tryptophan metabolism in 19 of the 20 leukemic children before and after tryptophan loading. Kynurenine, 3-hydroxykynurenine, and anthranilic and 3-hydroxyanthranilic acids appeared in urine, whereas 5-hydroxyindoleacetic acid was absent in the majority of the young patients. The disturbances of tryptophan metabolism were similar in all of them. Administration of vitamin Be restored tryptophan metabolism to normal in the majority of the patients. 

The spontaneous urinary pattern during viral hepatitis in an acute phase seems to be abnormal, showing kynurenine in a high percentage of cases together with 3-hydroxykynurenine, 3-hydroxyanthranilic acid, and in a few instances anthranilic acid. Some discrepancies appear for the excretion in clinically recovered subjects, since Quagliariello (Q3) found a normalized output of metabolites, whereas Piazza and Tancredi (P5) found that about 60% showed an abnormal excretion of the same substances. 

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. 

T3. Tompsett, S. L., The determination in urine of some metabolites of tryptophan-kynurenine, anthraniUc acid and 3-hydroxyanthranilic acid—and reference to the presence of o-aminophenol in urine. CZin. Chim. Acta 4, 411-419 (1959). 

The relation of many of the simpler alkaloids to the aromatic amino acids is obvious. For example, germinating barley contains (241), besides tyrosine and tyramine, A -methyltyramine, JViV -dimethyltyramine (hordenine), and the trimethylammonium derivative (candicine). In this simple case the. AT-methylated derivatives are known to be derivable from isotopically labeled tyramine (538) and the methyl groups are known to arise from methionine by transmethylation (540, 586). Similarly AT-methyl derivatives of phenylethylamine, 3,4-dihydroxyphenylethylamine, and 3,4,5-trihy-droxyphenylethylamine are well known alkaloids (cf. review, 701). N-Methylated derivatives of tryptamine and hydroxytryptamine equally occur for example, eserine has an obvious relation to 5-hydroxy tryptamine. Methylated derivatives of metabolites of the aromatic amino acids also occur, for example, trigonelline (67), which is the betaine of nicotinic acid, and damascenine is probably similarly related to hydroxyanthranilic acid. 

Figure 2 NAD biosynthesis subsystem diagram. Major functional roles are shown by 4-6 letter abbreviations (explained in Table 1) over the colored background reflecting the key aspects or modules (pathways) that comprise NAD biosynthesis in various species. Catalyzed reactions are shown by solid straight arrows, and corresponding intermediate metabolites are shown as abbreviations within ovals Asp, L-aspartate lA, Iminoaspartate Qa, quinolinic acid Nm, nicotinamide Na, nicotinic acid NaMN, nicotinic acid mononucleotide NMN, nicotinamide mononucleotide RNm, N-ribosyInicotinamide NaAD, nicotinate adenine dinucleotide NAD, nicotinamide adenine dinucleotide NADP, NAD-phosphate Trp, tryptophan FKyn, N-formylkynurenine Kyn, kynurenine HKyn, 3-hydroxykynurenine HAnt, 3-hydroxyanthranilate and ACMS, a-amino-/3-carboxymuconic semialdehyde. Unspecified reactions (including spontaneous transformation and transport) are shown by dashed arrows.

A stereoselective synthesis of tilivalline, a metabolite from klebsiella, has been achieved via intermediate 78 by coupling 3-hydroxyanthranilic acid (76) with pyrrolidine acetal (77).30... 

AMINOPHENOL-TYPE TRYPTOPHAN METABOLITES 3-HYDROXYKYNURENINE, 3-HYDROXYANTHRANILIC ACID, AND THEIR ROLE IN LIVING ORGANISMS... 

Pregnancy results in an increase in the urinary excretion of xanthurenic acid (B21, S18, VI, Wl), 3-hydroxykynurenine, kynurenine, acetylkynu-renine, 3-hydroxyanthranilic acid, 2-pyridone, and N -methylnicotina-mide (B21, H8, VI, Wl). Large doses of pyiidoxine may reduce the urine levels of these metabolites to or near the normal range (Wl, RIO). The findings in one study (H4), in which women early in preg-... 

The amino acid tryptophan is degraded by the higher plants to indolyl-3-acetic acid which is an important growth hormone for them, whereas bacteria usually degrade it to tryptamine, and mammals to 3-hydroxyanthranilic acid and thence to nicotinic acid which is an indispensable metabolite. 

Oat plant produced a group of secondary metabolites termed avenanthramides (avn), and has been biosynthesized by the enzyme action of hydroxycinnamoyl COA hydroxyanthranilate A-hydroxycinnamoyl transferase (HHT), which catalyzes the condensation of several cinnamate COA. Suspension cultures also produce large quantities of avnA and G by chitin elicitation. These findings suggest that the utility of oat suspension culture as a tool for more detailed investigation of the mechanisms trigger their biosynthesis as well as the factors dictating the particular types of avenanthramides biosynthesis (Wise et al. 2009). 

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