Tryptophan, tritiated

Allen, L. M., and W. R. Grover Tryptophan Tritiation in Supernatant Malate Dehydrogenase from Pig Heart. Biochem. Biophys. Res. Commun. 41, 1518-1522... 

ANSWER We used it in the 20 mg/kg twice a day for a 4-day regimen with MDMA, and then corrected for molecular weight and used an equimolar dose of MBDB, sacrificed the animals 2 weeks later, and then measured. We used basically HPLC and used serotonin and 5-HIAA from one hemisphere and then measured tritiated pyroxetine from the other hemisphere. And we got something like 60 percent depletion of serotonin, and the pyroxetine binding site decreased by about 60 percent. With MBDB it was decreased by about 40 percent. It was a clear and significant decrease, but not quite to the extent that we had. But we have not looked at tryptophan hydroxylase. 

C]Tryptophan gave inactive alkaloids but tritiated 2,4-dihydroxy-quinoline (34) and its N-methyl derivative were incorporated into (47) (0.009 % and 0.020% respectively) an early route had suggested the derivation of what was essentially (34) from tryptophan. Radioisotope dilution showed the presence of both these quinoline precursors together with iV-acetyl- and N-methyl-anthranilic acid in A. baueri. A satisfactory incorporation of N-methylanthranilic acid into (47) was found in Evodia xanthoxyloides, and this, together with its natural occurrence, indicates that early methylation may be important in the biosynthesis of acridone alkaloids. 

Our laboratory has studied the stereochemistry of methyl group formation in a number of a, 0 elimination reactions of amino acids catalyzed by pyridoxal phosphate enzymes. The reactions include the conversions of L-serine to pyruvate with tryptophan synthase 02 protein (78) and tryptophanase (79), of L-serine and l-tyrosine with tyrosine phenol-lyase (80), and l-cystine with S-alkylcysteine lyase (81). In the latter study, the stereospecific isotopically labeled L-cystines were obtained enzymatically by incubation of L-serines appropriately labeled in the 3-position with the enzyme O-acetyl serine sulfhy-drase (82). The serines tritiated in the 3-position were prepared enzymatically starting from [l-3H]glucose and [l-3H]mannose by a sequence of reactions of known stereochemistry (81). The cysteines were then incubated with 5-alkyl-cysteine lyase in 2H20 as outlined in Scheme 19. The pyruvate was trapped as lactate, which was oxidized with K2Cr202 to acetate for analysis. Similarly, Cheung and Walsh (71) examined the conversion of D-serine to pyruvate with... 

Cycloplazonic Acid. — Results pertaining to the incorporation into a-cyclopiazonic acid (79) of tryptophan chirally tritiated at C-3, previously published in a preliminary communication, are now available in a pull paper (c. Vol. 6,... 

The results with the tritiated tryptophan samples further indicate that hydrox-ylation at the carbon which corresponds to C-3 of tryptophan occurs with loss of the pro-R hydrogen, i.e. hydroxylation with retention of configuration. This result was probably to be expected for it is a well-founded rule that biological hydroxylation occurs with retention of configuration, and this then is an additional example from the field of secondary metabolites. 

The enzyme cysteine synthase (EC 4.2.99.8) catalyzes the last step in the biosynthesis of cysteine, converting serine acetate 97 to cysteine 134. Floss et al. (84) studied this -replacement reaction using stereospecifically tritiated serine acetates prepared from the labeled serines 60 synthesized as in Scheme 18 (Section IV). Assessment of chirality of the cysteine produced by degradation to serine and use of tryptophan synthase showed that the j3-replacement reaction 97a134 had proceeded with retention of configuration (84) (Scheme 45),... 

The chemical and enzymatic browning reactions of plant polyphenols and their effects on amino acids and proteins are reviewed. A model system of casein and oxidizing caffeic acid has been studied in more detail. The effects of pH, time, caffeic acid level and the presence or not of tyrosinase on the decrease of FDNB-reactive lysine are described. The chemical loss of lysine, methionine and tryptophan and the change in the bioavailability of these amino acids to rats has been evaluated in two systems pH 7.0 with tyrosinase and pH 10.0 without tyrosinase. At pH 10.0, reactive lysine was more reduced. At pH 7.0 plus tyrosinase methionine was more extensively oxidized to its sulphoxide. Tryptophan was not chemically reduced under either condition. At pH 10.0 there was a decrease in the protein digestibility which was responsible for a corresponding reduction in tryptophan availability and partly responsible for lower methionine availability. Metabolic transit of casein labelled with tritiated lysine treated under the same conditions indicated that the lower lysine availability in rats was due to a lower digestibility of the lysine-caffeoquinone complexes. 

Only a few studies have been made on the stereochemistry of dehydroamino acid formation in vivo. The biosynthetic elaboration of crypto-echinulin A (97) and mycelianamide 203, 204) has been the subject of feeding experiments with stereoselectively tritiated L-tryptophane and L-tyrosine respectively. Cw-dehydrogenation was established in both cases. 

Trisporic acids, Y19 Triterpenes, T42-53, T15-16 Tritiated compounds, Dl-2 Troger s Base, XI1 Tropane alkaloids, K28 Tropic acid, A41 Tropinic acid, A9 Tropin-2-one, K28 Tryptophan, A20 Tubaic acid, dihydro-, Y1 Tubercidin, Cl Tuberculostearic acid, A32 Tuberosin, Yl Tuberostemonine, K29 Tubifoline, K12 Tubocurarine, K2 ... 

Fig. 9. Incorporation of tritiated (T) and " C-Iabeled ( ) tryptophan into sporidesmin (25). The results of four separate double-labeling experiments are superimposed.

Tritiated tryptophan has been prepared by catalytic dehalogenation of the 5-bromo-derivative by Birkofer and Hempel 44). Labelling with tritium at the a- 62) and P-carbon 318) of tryptophan has been reported. Kirby and Varley 225) prepared tryptophan stereoselectively labelled with tritium and deuterium at the p-methylene group by using labelled 3-formyl indole as a starting compound (see also Section II.2.). 

Marche, P., J.-P. Girma, J.-L. Morgat, and P. Fromageot Specific Tritiation of Indole Derivatives by Catalytic Desulfenylation. Application to the Labelling of Tryptophan Containing Peptides. Eur. J. Biochem. 50, 375-382 (1975). 

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