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PubMed1975

[Dehydrogenase denaturation by guanidine hydrochloride measured by fluorescence (author's transl)].

Denaturation and subsequent renaturation of the enzymes Lactate, Glucose-6-phosphate, Glutamate and Alcohol dehydrogenases, by means of fluorescence spectra and the variation of enzyme activity in each conformational state, have been studied. The denaturating agent has been Guanidine chloride in a range of concentration from 0.5 to 6 M. Special behaviour has been observed in each enzyme in the presence of the denaturating agent. The action of this agent is compared with that of urea. The renaturation percentages obtained are relatively low. Interaction between the denaturating agent and the aminoacids producing the fluorescence of the enzymes is observed.

Alcohol Oxidoreductases↗
PubMed1999

Molecular characterisation of a NADH ubiquinone oxidoreductase subunit 5 from Schistosoma mansoni and inhibition of mitochondrial respiratory chain function by testosterone.

Complementary DNA, encoding the mitochondrial enzyme NADH-ubiquinone oxidoreductase subunit 5 (SmND5) of the human parasite Schistosoma mansoni was isolated by screening a S. mansoni cDNA library with a human androgen receptor (hAR) cDNA probe. The complete nucleotide and deduced aminoacid sequences of SmND5 were determined. Southern blot analysis revealed the occurrence of a single copy gene for SmND5 and by means of RT-PCR, it was shown that sex- and stage-specific expression of SmND5 occurred. In order to establish a functional relationship between the mitochondrial enzyme and the androgen receptor, the effects of testosterone were compared to those of classical respiratory chain inhibitors, using adult schistosome and beef heart submitochondrial particles. Physiological concentrations of testosterone were able to inhibit the maintenance of proton gradient across the mitochondrial membranes, as well as ATP synthesis. The steroid was found to be cytotoxic to the larvae, but not to adult schistosomes. A model is proposed to explain the observed in vivo testosterone-related differences in worm burdens, in experimental chronic infections.

Amino Acid Sequence↗
PubMed1988

Oxidative deamination of Se-(1-carboxyethyl)-,Se-(1-carboxypropyl)- and Se-(2-carboxyethyl)-selenocysteine by snake venom L-aminoacid oxidase.

Details are reported for the synthesis of Se-(1-carboxyethyl)-selenocysteine (1-CESeC), Se-(1-carboxypropyl)-selenocysteine (1-CPSeC) and Se-(2-carboxyethyl)-selenocysteine (2-CESeC). They can be obtained in pure cristalline form with good yield. Some chromatographic properties, useful for their identification, are described. The three aminoacids are good substrates for snake venom L-aminoacid oxidase, giving the corresponding alpha-ketoacids as reaction products.

Amino Acid Oxidoreductases↗
PubMed1978

Oxidative deamination of carboxyethyl-cysteine and carboxymethyl-homocysteine.

Snake venom L-aminoacid oxidase, while inactive on 4C and 5C dicarboxylic alpha-amino acids, may oxidize their 6C and 7C homologues alpha-aminoadipic and alpha-aminopimelic acid. It has been demonstrated that the enzyme also oxidizes S-carboxyethyl-L-cysteine and S-carboxymethyl-L-homocysteine, two analogues of alpha-aminopimelic acid with the gamma or delta methylene groups substituted by a sulfur atom. As oxidation products the corresponding ketoacids were obtained. Thus substrate specificity of L-aminoacid oxidase for dicarboxylic alpha-aminoacids seems highly dependent on the carbon chain length, whereas substitution of a methylene group by a sulfur atom seems to have almost no effect. On the other hand, D-aspartate oxidase from beef kidney (active on 4C to 6C dicarboxylic alpha-aminoacids) cannot oxidize the 7C alpha-aminopimelic acid but is active on the S-carboxyethyl-D-cysteine analogue. The other aminopimelic analogue, S-carboxymethyl-D-homocysteine, is a very poor substrate. Thus the substrate specificity of D-aspartate oxidase, highly dependent on chain length, is also influenced by chain conformation. Furthermore, oxidation of either compound under study, L-aminoacid oxidase and D-aspartate oxidase, leaves unaffected the thioether bond.

Amino Acid Oxidoreductases↗
PubMed1980

The activities of peroxisomal oxidases in periportal and perivenous zones of the rat liver acinus.

Using a new biological microassay the activities of three peroxisomal oxidases in single microdissected periportal and perivenous zones of the liver acinus were measured. Whereas urate oxidase is homogeneously distributed through the acinus, the activities of D-aminoacid oxidase and alpha-hydroxyacid oxidase are respectively 1.80- and 2.71-fold higher in the periportal hepatocytes than in the perivenous hepatocytes.

Alcohol Oxidoreductases↗
PubMed2003

The enol tautomer of indole-3-pyruvic acid as a biological switch in stress responses.

Indole-3-pyruvic acid (IPA) undergoes in solutions to the keto-enol tautomerism, which appears responsible of its pharmacological effects, as only the enol tautomer is an easy target for oxygen free-radicals and can be transformed directly to kynurenic acid (KYNA). Contrary to expectations, the IPA enol tautomer is rather stable in mammalian tissues, due to the presence of specific tautomerases, favouring the formation of KYNA in the presence of free-radicals. Because of the synergistic effects between glucocorticoids, free-radicals and excitatory aminoacids in chronic stress, the enol tautomer of IPA and KYNA are proposed as physiological metabolites produced in order to shut-off the chronic stress cycle.

Animals↗
PubMed1979

Biotransformation of chloroform by rat and human liver microsomes; in vitro effect on some enzyme activities and mechanism of irreversible binding to macromolecules.

The effects of chloroform on some rat microsomal enzyme activities were studied in vitro. Maximum inhibition of oxygen consumption, NADPH oxidase and NADPH-cytochrome c reductase was observed at 0.5 mM chloroform; prior metabolization of CHCl3 by microsomal monooxygenases increased inhibition by about 50% at 0.2-0.5 mM chloroform. Higher concentrations produced a paradoxical reversal of inhibition, whereas p-nitroanisole demethylase was steadily inhibited by about 50% up to 10 mM chloroform. Irreversible binding of 14CHCl3 was confirmed to depend on chloroform metabolization by monooxygenases. The increased irreversible binding due to phenobarbital induction is accompanied by a diminished affinity towards chloroform as shown by increased KM of irreversible binding, and a higher spectral dissociation constant KS. Aminoacids with nucleophilic functions (histidine, cysteine) partially prevented the irreversible binding of chloroform metabolites to microsomes; non-volatile radioactive derivatives were recovered in trichloracetic acid supernatants when microsomes were incubated with cysteine, but not with histidine. Phosgene has been demonstrated as a biological metabolite of chloroform: its possible reactions with nucleophilic groups of macromolecules, water and added aminoacids partly explain these experimental data. Similar results were obtained with human microsomes, showing that chloroform hepatotoxicity in man could involve the same mechanisms.

Animals↗
PubMed2003

Multinuclear NMR investigations on the metabolic recovery of the isolated perfused mouse liver after cold preservation.

This paper describes multinuclear NMR investigations on the isolated perfused mouse liver to optimize its recovery after cold preservation and normothermic reperfusion. The recovery of livers from fed is better than that from 24 h fasted animals. This better recovery is not due to a higher glycogen content before cold preservation. The recovery of livers from fasted animals is specifically enhanced by the presence of 8 mM alanine in the rinsing solution after cold preservation and in the perfusate of reperfusion. This property is not due to the ability of alanine to compensate for the lack of endogenous substrates since the amount, before cold preservation, of these substrates, is not significantly different in livers from fed and fasted animals. Furthermore, the beneficial effect of alanine is not due to an enhancement of the pyruvate dehydrogenase (PDH) activity in livers from fasted animals. In fact these livers have indeed a smaller PDH activity than the livers from fed animals but dichloroacetate, a known PDH activator has a rather deleterious effect on the recovery of fed and fasted livers. Furthermore alanine protects the fasted livers against this effect. So the beneficial effect of alanine should be due to other causes. Furthermore, we have found on a parallel model of rat isolated perfused liver, that the recovery of steatotic livers which is lower than that of normal fed livers is enhanced by a known vasodilator, pentoxifylin but not by alanine. So alanine does not either play its role through its action on microcirculation. The interaction of alanine with some membrane sodium transporters like that already reported for another protective aminoacid, glycine, is thus possible. A novel NMR method of (23)Na observation in living cells or organs should be of great interest to investigate this hypothesis.

Alanine↗
PubMedDate not supplied

Carboxymethyl-selenopyruvic acid as the product of the oxidative deamination of carboxymethyl-selenocysteine.

CMSeC labeled with 14C in the carboxymethyl moiety was incubated with snake venom L-aminoacid oxidase. As the product of the reaction only one ketoacid was detected, which retained all the radioactivity of the oxidized substrate. This clearly shows that no breakdown of the C-Se bond of CMSeC occurs during its oxidation, and confirms previously reported data indicating that the ketoacid arising from CMSeC is CMSeP.

Amino Acid Oxidoreductases↗