Showing papers on "Methylglyoxal published in 1987"

Metabolism of 2-oxoaldehydes in bacteria: purification and characterization of methylglyoxal reductase from Escherichia coli

Abstract: The activities of 2-oxoaldehyde-metabolizing enzymes (glyoxalase I, glyoxalase II, methyl- glyoxal reductase, methylglyoxal dehydrogenase and lactaldehyde dehydrogenase) were found to be widely distributed among microorganisms. One of the enzymes, methylglyoxal reductase, which catalyzes the reductive conversion of methylglyoxal into lactaldehyde, was purified from Escherichia coli cells. The enzyme was judged to be homogeneous on polyacrylamide gel electrophoresis and was a monomer with a molecular weight of 43000. The enzyme was most active at pH 6.5 and 45°C. The enzyme utilized both NADPH and NADH for the reduction of 2- oxoaldehydes (glyoxal, methylglyoxal, phenylglyoxal and 4,5-dioxovalerate) and some aldehydes (glycolaldehyde, D,l-glyceraldehyde, propionaldehyde and acetaldehyde). The Km values of the enzyme for methylglyoxal, NADPH and NADH were 4.0 mm, 1.7 fiM and 2.8 /?m, respectively. The product of methylglyoxal reduction was identified as lactaldehyde. The enzyme from E. coli cells was differ...

Methylglyoxal-induced mutation to 6-thioguanine resistance in V79 cells

Abstract: Methylglyoxal, at concentrations ranging from 0.16 to 1.5 mM, caused a dose-dependent increase in the frequency of HGPRT-deficient mutants in V79 cells. Its mutagenic activity was reduced when V79 cells were co-cultured with freshly isolated rat hepatocytes.

Metabolism of 2-ketoaldehydes in mold: purification and characterization of glyoxalase I from Aspergillus niger.

Abstract: Glyoxalase I catalyzing the conversion of methylglyoxal into S-lactoylglutathione in the presence of glutathione was purified approximately 1,400-fold with 2.9% activity yield from mold, Aspergillus niger. The enzyme consisted of a single polypeptide chain with a relative molecular weight of 36,000 on both SDS-polyacrylamide gel electrophoresis and Sephadex G-150 gel filtration. The enzyme was most active at pH 7.0, 35-37 degrees C. Among the various aldehydes tested, the enzyme was active on methylglyoxal and 4,5-dioxovalerate with Km values of 1.25 and 0.87 mM, respectively. The activity of the enzyme was completely inhibited by Zn2+ at 0.5 mM. An equimolar amount of EDTA (0.5 mM) protected the enzyme from inactivation by Zn2+. EDTA competitively (K1 = 1.3 mM) inhibited the activity of the enzyme. Fe2+ was a potent activator for the enzyme, the activation being approximately 2.4-fold at 0.5 mM.

Isolation of Variants Resistant to Methylglyoxal Bis(guanylhydrazone) from Adenovirus-transformed Rat Cells

Abstract: It is presumed that proteins encoded by viral oncogenes interact with proteins encoded by cellular genes to bring about the transformed phenotype. To demonstrate the existence of such cellular genes we attempted to isolate mutants with a nontransformed phenotype from an adenovirus-transformed rat cell line (F4) which contains multiple copies of the transforming E1 region. F4 cells were mutagenized with ethyl methane-sulfonate and variants resistant to the anticancer drug methylglyoxal bis(guanylhydrazone) were selected. The proportion of such variants was about one in 106 and increased 5-fold after mutagenesis. Two variant clones (G1 and G2) were isolated and characterized: ( a ) they were 5-fold more resistant to methylglyoxal bis(guanylhydrazone); ( b ) they had a stable phenotype; ( c ) they showed decreased drug uptake; ( d ) they had a reduced ability to grow in soft agar, low serum, and nude mice; ( e ) there was no detectable change in the restriction pattern of integrated viral genes or in the expression of the E1a and E1b proteins. These properties suggest that selection for methylglyoxal bis(guanylhydrazone) resistance may result in the isolation of variants with phenotypic characteristics of nontransformed cells. It was likely that these variants were altered in a cellular function required for the maintenance of the transformed phenotype.

Methylglyoxal: genotoxicity studies and its effect in vivo on the hepatic microsomal mono-oxygenase system of the mouse.

Abstract: The genotoxic potential of methylglyoxal (MG) was studied in Saccharomyces cerevisiae D7 and in Salmonella typhimurium TA97 and TA102 in the presence and in the absence of metabolic activation system (S9 fraction) prepared from mouse liver induced with beta-naphthoflavone (beta-NF) and sodium phenobarbital (PB). The in vivo effects on the hepatic microsomal mixed function mono-oxygenase system induced by MG were studied in untreated, beta-NF or PB pre-treated mice. MG was a direct-acting mutagen in S. typhimurium TA97 and TA102 when tested up to a maximum concentration of 0.47 mg/plate. Mitotic gene conversion was also induced by MG in the yeast S. cerevisiae D7. A weak but significant effect on reverse point mutation was also found in S. cerevisiae. Genetic activity was lower in the presence of S9 fraction in yeast test. In the in vivo studies, MG (at the total dose of 600 mg/kg) was shown to increase the aminopyrine N-demethylase (APD) and p-nitroanisole O-demethylase (p-NAD) activities in uninduced mice. Cytochrome P-450 content (cyt P-450) and ethoxycoumarin O-deethylase activity (ECD) were also weakly enhanced by MG treatment. In contrast, no significant changes in mono-oxygenase activities were seen in beta-NF- or PB-treated mice after MG injection.

Metabolism of 2-Ketoaldehydes in Bacteria: Oxidative Conversion of Methylglyoxal to Pyruvate by an Enzyme from Pseudomonas putida

Abstract: Enzymes that catalyze the oxidation or reduction of methylglyoxal were screened for in several prokaryotic and eukaryotic microorganisms. Methylglyoxal-reducing activity was found to be widely distributed at considerably high levels in microorganisms. Methylglyoxal-oxidizing activity was detected only in cells of Pseudomonas putida among the organisms examined. The enzyme responsible for the methylglyoxal oxidation was purified approximately 240 fold from a cell extract of P. putida. The enzyme consisted of a single polypeptide chain with a molecular weight of 42,000 and showed a pH optimum of 8.0. The enzyme was active on 2-ketoaldehydes [glyoxal, methylglyoxal (Km = 1.0 mm) and phenylglyoxal] and some aldehydes (formaldehyde, acetaldehyde, glycolaldehyde and propionaldehyde) in the presence of NAD (^m = 0.1mm). The bacterial methylglyoxal-oxidizing enzyme appeared similar to goat liver 2-ketoaldehyde dehydrogenase in molecular weight and structure, but was different in its substrate affinity.

Polyamine metabolism as a target for growth inhibition of Acanthamoeba culbertsoni.

Abstract: Alpha-difluoromethylornithine had no inhibitory effect on the growth of Acanthamoeba culbertsoni, while methylglyoxal bis(guanyl-hydrazone) and sinefungin completely blocked amebic growth at 2.5 mM and 5 micrograms/ml concentrations, respectively. Cyclohexylamine caused only partial inhibition of amebic growth at 50-200 microM concentrations. Methylglyoxal bis(guanyl-hydrazone) inhibited S-adenosylmethionine decarboxylase of A. culbertsoni indicating this enzyme to be the target for its antiamebic action. This enzyme was, however, not inhibited by sinefungin, suggesting an alternative target for growth inhibition by this compound.

From methylglyoxal to new immunopotentiating ascorbic acid derivatives.

Abstract: In Szent-Gyorgyi's search for alpha-dicarbonyl compounds that play an important role in cell regulation, 3-desoxyglucosulose was isolated first from liver but did not prove active. Methylglyoxal came next, however, its toxicity prompted Szent-Gyorgyi to suggest a combination with ascorbic acid which, indeed led to immunopotentiating enediol acetals although of low stability. Therefore the vinylogue of methylglyoxal, acetylacrolein was coupled with L-ascorbic acid carbanion. This second new reaction, of the aldol-type, led to the stable, potent immunoactive compound, 2-(5-methylfuryl)-3-ketogulonolactone cyclohemiketal that forms a completely surprising H-bond with succinic anhydride and succinimide based on an X-ray study. A third new reaction in which ascorbic acid plays the role of a Michael donor to alpha,beta-unsaturated aldehydes and ketones proved now to be of general validity; it is unexpectedly acid catalyzed and the adducts formed with aliphatic and alicyclic olefin ketones have definite immunopotentiating effect. A brief description of the biological effects of all types of new compounds is outlined.

Production of 4-methylimidazoles

Abstract: PURPOSE: To obtain 4-methylimidazoles on an industrial scale at a low cost in high yield, by reacting an aldehyde with ammonia in an aqueous medium, adding methylglyoxal to the reaction system and continuing the reaction. CONSTITUTION: An aldehyde and ammonia are introduced into an aqueous medium and are made to react with each other preferably at about 15W30°C. Subsequently, methylglyoxal is charged to the system (preferably by dripping) and the reaction is continued at 15W30°C to obtain 4-methylimidazole. The compound is useful as an intermediate for organic chemicals such as various pharmaceuticals, agricultural chemicals, etc., and as an epoxy resin hardener. COPYRIGHT: (C)1988,JPO&Japio

A reinvestigation of inhibitors of glyoxalase I

Abstract: It has been reported earlier that nucleotides, nucleosides and a series of structurally related compounds as well as compounds based on transition state analogy inhibit yeast glyoxalase I. In our study on the metabolic regulation of glyoxalase I, we have found that nucleotides such as ATP, GTP and different classes of other reagents based on transition state analogy (D-isoascorbate, dihydroxyfumaric acid, rhodizonic acid) do not inhibit yeast or goat liver glyoxalase I. The reported inhibition of glyoxalase I by these compounds has been found to be due to the interference of these compounds with the absorbancy at 240 nm of S-D-lactoylglutathione formed by the glyoxalase I reaction.

Effect of Altered Inflation on Pulmonary Uptake of Methylglyoxal Bis(Guanylhydrazone)

Abstract: The effects of increased pulmonary ventilation on uptake of an exogenous, nonme-tabolized polyamine analog, methylglyoxal bis(guanylhydrazone) [MGBG] were investigated in rat lungs perfused in situ with buffer containing 4.5% bovine serum albumin, 5.6 mM glucose and plasma levels ofamino acids. The perfusate was equilibrated and the lungs were ventilated with warmed, humidified O2/N2/CO2 (20:75:5). A 28% increase in lung inflation rapidly accelerated MGBG uptake at low (1.5 μM) but not at high (50 μM) substrate concentration, a change which appeared to reflect a decrease in the apparent Km of the uptake pathway. This effect was not associated with acute alterations in pulmonary vascular permeability or resistance, nor with instability of the preparations. Taken with observations made previously, these results suggest that deformation of the tissue by increased inflation may account for increased MGBG uptake by lungs from rats subjected to partial pneumonectomy.

Effects of methylglyoxal bis(guanylhydrazone) and two phenylated analogues on S-adenosylmethionine decarboxylase activity from Eimeria stiedai (Apicomplexa).

Abstract: 1. Activity of S-adenosylmethionine decarboxylase, one of the rate-limiting enzymes of polyamine biosynthesis, was determined in oocysts of Eimeria stiedai, a coccidian parasite of the rabbit. 2. Several properties of the enzyme were compared to the mammalian enzyme. It showed considerably less substrate affinity than the analog enzyme from the rabbit. 3. The E. stiedai enzyme showed a low sensitivity to methylglyoxal bis(guanylhydrazone), a frequently used inhibitor of the enzyme in mammals, and two phenylated derivatives. 4. Results with the inhibitors are discussed in view of their potential use in chemotherapy.