Showing papers on "Methylglyoxal published in 1982"

Mutagenicity of Methylglyoxal in Coffee

Abstract: Major carbonyl compounds from a extract of ground roasted coffee beans were identified as 5-hydroxymethylfurfural, acetol, glyoxal, methylglyoxal and diacetyl. Among these carbonyl compounds, methylglyoxal showed considerable mutagenic activity toward Salmonella typhimurium TA100 without S9 mix (around 100,000 revertants/mg). More than 50% of the total mutagenic activity of coffee can be accounted for by the activity of methylglyoxal.

Comparison of S-adenosylmethionine decarboxylases from rat liver and muscle.

Abstract: S-Adenosylmethionine decarboxylase was purified to homogeneity from rat liver and from rat psoas. The major step involved affinity chromatography on methylglyoxal bis-(guanylhydrazone) linked to Sepharose. The muscle enzyme was more tightly retained to this absorbent, and the enzymes from the two sources could readily be separated by chromatography on this material. The psoas and liver enzymes could not be distinguished by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, both giving a single band corresponding to an Mr of 32 500, but were separated by electrophoresis under nondenaturing conditions and by isoelectric focusing (the isoelectric points were 5.3 for psoas and 5.7 for liver enzyme). The liver and psoas enzymes also differed in respect to Km for S-adenosylmethionine, the degree to which they were activated by putrescine, and their sensitivity to inhibition by methylglyoxal bis(guanylhydrazone) and related compounds. These results indicate that there are two forms of S-adenosylmethionine decarboxylase. The presence of a particular form could, therefore, be important both in the regulation of polyamine levels and also in the pharmacology involving inhibitors of polyamine synthesis.

Neutrophil chemotactic responses to aldehydes.

Abstract: The influence of 4-hydroxynonenal (HNE), 4-hydroxytetradecenal (HTDE) and methylglyoxal (MGL) on rat polymorphonuclear leukocyte locomotion has been studied by means of boyden chambers. The two alkenals have been found to exert a chemotactic activity in a range of concentrations between 10-9 and 10-5 M, the most potent chemical being HTDE. The chemotactic effect, however, appeared influenced by the concentration of serum albumin in the medium. In addition, chemotactic doses of the same aldehydes were unable to affect the cell random migration. Higher concentrations of these alkenals depressed both the directed and random locomotion. Methylglyoxal appeared deprived of chemotactic power when assayed at the doses that were active with the above mentioned alkenals and it did not interfere with random migration. 5 X 10-4 M Methylglyoxal exerted a slight, but significant, inhibition of the locomotion events. These results suggest that aldehydes, present at the inflammatory sites, as final products of lipid peroxidation, might play a role in modulating the granulocyte cell locomotion, therefore interfering with the development of phlogosis.

Delayed Sensitization to Heat by Inhibitors of Polyamine-biosynthetic Enzymes

Abstract: Exposure of Chinese hamster ovary cells to the enzyme inhibitors methylglyoxal bis(guanylhydrazone and alpha-difluoromethylornithine (DFMO) results in increased sensitivity to hyperthermia. While methylglyoxal bis(guanylhydrazone) demonstrates pronounced cytotoxicity at moderate extracellular concentrations, DFMO is tolerated well by this cell line at concentrations of up to 10 mM, as assayed by clonogenic survival after treatments at 37 degrees. An 8-hr preincubation at 37 degrees with either drug elicits increasing sensitivity to 43 degrees hyperthermia treatments with time after removal of the drug. In contrast to results obtained by heating in the presence of the drugs during the 8-hr exposure, DFMO acts as the more effective sensitizing agent for this delayed effect on progeny of DFMO-treated populations. This phenomenon seems to result from depletion of intracellular putrescine, because the effect can be at least partially recovered by providing the cells with an exogenous source of this diamine. The potential for in vivo heat sensitization by the non-toxic agent DFMO has yet to be investigated but may have intriguing clinical possibilities.

Glyoxalase I from human erythrocytes.

Abstract: Publisher Summary Glyoxalase I catalyzes the formation of S-2-hydroxyacylglutathione from 2-oxoaldehydes, such as methylglyoxal and glutathione (GSH). This chapter describes the assay method, the purification procedure, and the properties of glyoxalase I isolated from human erythrocytes. Human glyoxalase I exists in the form of three isozymes that appear identical in their functional properties. The increase in absorbance at 240 nm because of thiolester formation from glutathione (GSH) and methylglyoxal is monitored spectrophotometrically. The purification procedure involves denaturation of hemoglobin, acetone fractionation, ammonium sulfate fractionation, affinity chromatography (I) on S-Hexylglutathione-Sepharose 6B, chromatography on Sephadex G-75, affinity chromatography II, chromatography on diethylaminoethyl (DEAE)-Sepharose, and separation of isozymes of glyoxalase I. The enzyme obtained by this procedure appears homogeneous as judged by various analytical procedures, except for the presence of the three isozymes. The enzyme is composed of two subunits of equal weight and contains one Zn per subunit that is essential to catalytic activity.

Formation of the thioester, N-acetyl, S-lactoylcysteine, by reaction of N-acetylcysteine with pyruvaldehyde in aqueous solution

Abstract: N-acetylcysteine reacts efficiently with pyruvaldehyde (methylglyoxal) in aqueous solution (pH 7.0) in the presence of a weak base, like imidazole or phosphate, to give the thioester, N-acetyl, S-lactoylcysteine. Reactions of 100 mM N-acetylcysteine with 14 mM, 24 mM and 41 mM pyruvaldehyde yield, respectively, 86%, 76% and 59% N-acetyl, S-lactoylcysteine based on pyruvaldehyde. The decrease in the percent yield at higher pyruvaldehyde concentrations suggests that during its formation the thioester is not only consumed by hydrolysis, but also by reaction with some substance in the pyruvaldehyde preparation. Indeed, purified N-acetyl, S-lactoylcysteine disappears much more rapidly in the presence of pyruvaldehyde than in its absence. Presumably, N-acetyl, S-lactoylcysteine synthesis occurs by rearrangement of the hemithioacetal of N-acetylcysteine and pyruvaldehyde. The significance of this pathway of thioester formation to molecular evolution is discussed.

The glyoxalase system in rat blood.

Abstract: The 3-carbon keto-aldehyde, methylglyoxal (MeG), inhibits growth in bacterial and mammalian systems. The glyoxalase enzyme system catalyzes the catabolism of the α,β-dicarbonyl to form d-lactate with glutathione (GSH) as a cofactor. Glyoxalase I (S-lactoyl-glutathione methylglyoxal-lyase, isomerizing; EC 4.4.1.5) and glyoxalase II (S-2-hydroxyacylglutathione hydrolase; EC 3.1.2.6) are present in mammalian tissues and have a high specific activity in red blood cells. In order to determine possible changes in the glyoxalase system with growth, the various components of the glyoxalase system were measured in the blood of male Sprague–Dawley rats aged 20 to 89 days. Glyoxalase I and II kinetic parameters were determined in potassium phosphate buffer at pH 6.8. Glutathione reductase activity, blood concentration of GSH and protein, plasma concentration of d-lactate, and hematocrit were also measured. The mean V for glyoxalase I was 81 μmole·mhr-1·ml-1 of red blood cells as compared to the glyoxalase II...

2-Ketoaldehyde dehydrogenase from rat liver.

Abstract: Publisher Summary This chapter discusses a scheme for the purification of 2-oxoaldehyde dehydrogenase from the rat liver and an assay procedure that uses L-serine methyl ester as an activating amine. The dehydrogenase from the rat liver appears to be specific both for nicotinamide adenine dinucleotide phosphate kinase (NADP + ) and for methylglyoxal. 2-Ketoaldehyde dehydrogenase is assayed in 0.1 M sodium pyrophosphate buffer, pH 9, containing 0.5 m M NADP + , 5 m M methylglyoxal, and 50 m M L-serine methyl ester. Background activity at 340 nm and 25°C temperature is monitored for 1 min prior to the addition of the enzyme sample. One unit of activity corresponds to the production of 1 μ mol of nicotinamide adenine dinucleotide phosphate dehydrogenase (NADPH) per minute. The steps involved in the purification of the enzyme are also discussed in the chapter. The use of DL-2-amino-1-propanol in place of L-serine methyl ester gives equally effective activation of 2-ketoaldehyde dehydrogenase from the rat liver.

Oxidation, photosensitized by certain diketones, of enzymes and protection against such oxidation by histidine derivatives.

Abstract: Bovine milk lactoperoxidase, eel acetylcholinesterase, and Aeromonas aminopeptidase were photooxidized and inactivated in broad-spectrum visible light in the presence of 2,3-butanedione and l-phenyl-l,2-propanedione. Methylglyoxal caused similar effects at 25zt nm. 2-Thiol-L-histidine and 3-methyl-L=histidine protected the enzymes against photoinactivation more effectively than N3−, even at a molar ratio of 2:1 (protector to enzyme). These compounds also delayed the photoinactivation of acetylcholinesterase, induced by ultraviolet light.

Combined topical use of difluoromethyl ornithine and methylglyoxal bis (guanylhydrazone) in UV-irradiated mouse skin.

Abstract: SUMMARY Topical application of difluoromethyl ornithine, an irreversible inhibitor of ornithine decar-boxylase, on UV-irradiated mouse skin, reduced epidermal putrescine and spermidine contents and greatly enhanced the epidermal uptake of subsequently applied methylglyoxal bis(guanyl-hydrazone). High epidermal concentrations of methylglyoxal bis (guanylhydrazone) could effectively be lowered by a single application of an ointment containing spermidine. The present results indicate that difluoromethylornithine and methylglyoxal bis (guanylhydrazone) pene trate mammalian skin from topical ointments, and that, in case of a too high (toxic) methylglyoxal bis (guanylhydrazone) concentration, spermidine can be used as a ‘rescuing’ agent.