Showing papers on "Methylglyoxal published in 1989"

A product study of the gas‐phase reaction of methyl vinyl ketone with the OH radical in the presence of NOx

Abstract: The gas-phase reaction of methyl vinyl ketone with the OH radical, in the presence of NOx, was investigated at 298 ± 2 K and atmospheric pressure of air. Glycolaldehyde and methylglyoxal were observed to be the major products, with a combined yield of 0.89 ± 0.16. The sum of the yields of the two other main products, formaldehyde and peroxyacetyl nitrate, were found to be essentially unity. The product yield data for glycolaldehyde and methylglyoxal indicate that OH radical addition to the terminal carbon atom of the >CC< bond accounts for 72 ± 21% of the overall reaction, with the remaining 28 ± 9% proceeding via addition to the inner carbon atom of the double bond.

Inhibition of the glycolytic pathway by methylglyoxal in human platelets.

Abstract: The incubation of human platelets with methylglyoxal and glucose produces a rapid transformation of the ketoaldehyde to D-lactate by the glyoxalase system and a partial reduction in GSH. Glucose utilization is affected at the level of the glycolytic pathway. No effect of the ketoaldehyde on glycogenolysis and glucose oxidation through the hexose monophosphate shunt was demonstrated. Phosphofructokinase, fructose 1,6 diphosphate (F1, 6DP) aldolase, glyceraldehyde 3-phosphate dehydrogenase and 3-phosphoglycerate mutase were mostly inhibited by methylglyoxal. A decrease in lactate and pyruvate formation and an accumulation of some glycolytic intermediates (fructose 1,6 diphosphate, dihydroxyacetone phosphate, 3-phosphoglycerate) was observed. Moreover methylglyoxal induced a fall in the metabolic ATP concentration. Since methylglyoxal is an intermediate of the glycolytic bypass system from dihydroxyacetone phosphate to D-lactate, it may be assumed that ketoaldehyde exerts a regulating effect on triose metabolism.

Effects of glyoxal and methylglyoxal administration on gastric carcinogenesis in Wistar rats after initiation with N-methyl-N'-nitro-N-nitrosoguanidine.

Abstract: Glyoxal and methylglyoxal were tested for tumor-promoting potential in a two-stage stomach carcinogenesis model. Male outbred Wistar rats were initially given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water (100 mg/l) along with a 10% sodium chloride dietary supplement for 8 weeks. Thereafter, they were returned to basal diet and maintained on drinking water containing no addition or either 0.5% glyoxal or 0.25% methylglyoxal for 32 weeks and then killed for necropsy and histological examination at week 40. Glyoxal treatment significantly increased the incidence of adenocarcinomas in the pylorus of the glandular stomach of rats pretreated with MNNG and sodium chloride. Furthermore, although methylglyoxal did not enhance the development of adenocarcinomas, the incidence of hyperplasias in the pylorus was significantly increased. The results indicate that glyoxal exerts tumor promoting activity on rat glandular stomach carcinogenesis and that methylglyoxal might also have promoting potential.

2-Oxoaldehyde metabolism in microorganisms.

Abstract: The properties of methylglyoxal-metabolizing enzymes in prokaryotic and eukaryotic microorganisms were studied systematically and compared with those of mammalian enzymes. The enzymes constitute a glycolytic bypass and convert methylglyoxal into pyruvate via lactate. The first step in this conversion is catalyzed by glyoxalase I, methylglyoxal reductase, or methylglyoxal dehydrogenase. The regulation of the yeast glyoxalase system was analyzed. The system was closely related to the proliferative states of yeast cells, the activity of the system being high in dividing cells and low in nondividing ones. The gene for the glyoxalase I of Pseudomonas putida and the genes responsible for the activity of glyoxalase I and methylglyoxal reductase in Saccharomyces cerevisiae were cloned and their structural and phenotypic characters studied.Key words: 2-oxoaldehydes metabolism, regulation of glyoxalase system, cloning, glyoxalase I gene, methylglyoxal reductase gene, methylglyoxal metabolism.

Formation of methylglyoxal by bacteria isolated from human faeces.

Abstract: Bacteria present in the human gut may produce methylglyoxal—a cytotoxic substance in mammals. This was investigated by studying the activity of methylglyoxal synthase, which produces methylglyoxal from dihydroxyacetone phosphate, and methylglyoxal concentration in growth medium of various bacteria isolated from human faeces. Facultative and strictly anaerobic bacteria isolated from faeces were able to produce methylglyoxal in both defined and complex media. Proteus spp. produced large amounts of methylglyoxal and had the greatest methylglyoxal synthase activity. Supplementing defined medium for facultative anaerobes with glucose 1% w/v did not significantly alter enzyme activity or methylglyoxal production. Inclusion of short chain fatty acids or bile acids in the medium reduced methylglyoxal synthase activity and methylglyoxal production by Proteus spp. None of the organisms examined had amine oxidase activity which could have contributed to methylglyoxal production from aminoacetone.

Erythrocyte glyoxalase activity in genetically obese (ob/ob) and streptozotocin diabetic mice.

Abstract: Hyperglycemia associated with the manifestation of the obese diabetic (ob/ob) syndrome in mice and the short and long term streptozotocin treatment of lean MF1 mice was accompanied by a significant decrease in erythrocyte glyoxalase 1 activity and a marked increase in the concentration of the alpha-oxoaldehyde methylglyoxal. Erythrocyte glyoxalase II activity was modestly but significantly elevated in both obese mice and short term streptozotocin treated MF1 mice but no significant changes in S-D-lactoylglutathione concentration could be detected. Modification of the cells glyoxalase system during hyperglycaemia, especially the enhanced production of methylglyoxal may be a significant biochemical factor in the development of diabetic complications.

Non-p-glycoprotein-mediated multidrug resistance in detransformed rat cells selected for resistance to methylglyoxal bis(guanylhydrazone).

Abstract: Three independent variants (G2, G4, G5), resistant to methylglyoxal bis(guanylhydrazone), an anticancer drug, have been isolated by single step selection from an adenovirus-transformed rat brain cell line (1). These variants display selective cross-resistance to several natural product drugs of dissimilar structure and action. Multidrug resistance has recently been shown to be caused by overexpression of the membrane-associated p-glycoprotein, most often caused by amplification of the mdr gene. Several types of experiments were conducted to determine whether the observed drug resistance in our cell lines could be due to changes at the mdr locus. The following results were obtained: (a) the mdr locus was not amplified; (b) transcription of the mdr gene and p-glycoprotein synthesis were not increased; (c) multidrug resistance cell lines, which carry an amplified mdr locus, were not cross-resistant to methylglyoxal bis(guanylhydrazone); (d) verapamil did not reverse the resistance of G cells or mdr cells to methylglyoxal bis(guanylhydrazone), nor that of G cells to vincristine; and (e) methylglyoxal bis(guanylhydrazone) resistance was recessive and depended on a block to drug uptake, as opposed to mdr cells which are dominant and express increased drug efflux. The results obtained suggest that the drug resistance in the G2, G4, and G5 cells was atypical and may be due to a mechanism distinct from that mediated by the mdr locus.

Potentiation of cis-dichlorodiammineplatinum (II)-induced cytotoxicity by methylglyoxal.

Abstract: The dicarbonyl compound methylglyoxal (MG) potentiated the cell inactivating effect of cis-dichlorodiammine-platinum (II) (cis-DDP) when cultured human NHIK 3025 cells were treated with both drugs in simultaneous combination. While a 2 h treatment with cis-DDP alone resulted in a surviving fraction of 0.024 +/- 0.008, the simultaneous presence of 0.5 mM MG, a non-cytotoxic concentration, reduced the fraction of cells surviving treatment to 0.0009 +/- 0.0001. Although the cell inactivating effect of cis-DDP was potentiated, the amount of cell-associated platinum was not affected by MG. Glyoxal, another dicarbonyl compound, did not affect cis-DDP-induced cytotoxicity in any manner, nor did the aliphatic aldehydes acetaldehyde and propionaldehyde. Cell inactivation induced by MG alone at concentrations above 0.5 mM could be prevented by the simultaneous presence of cysteine or glutathione, indicating that cellular sulfhydryls may be involved in the expression of MG-induced cytotoxicity. Furthermore, MG-induced cell inactivation was increased by a dose-modifying factor of 2.6 when NHIK 3025 cells were first pretreated with buthionine sulfoximine, a glutathione synthesis inhibiting compound. We propose that MG reacts with cellular sulfhydryls which may also be involved in the mediation of cis-DDP cytotoxicity. Reactions between cellular sulfhydryls and MG therefore increase the cytotoxicity of cis-DDP by allowing more platinum to react with cellular targets, not by increasing the amount of platinum entering cells.

A Method for the Determination of a-Dicarbonyl Compounds 1

Abstract: AB~rFIAOT A method is reported for determining the t~-dicarbonyls glyoxal, methylglyoxal, and diacetyl. The carbonyls were reacted at pH 8 with .05% aqueous solution of ophenylenediamine for 4 h at 25"C to form quinoxalines. The derivatives were extracted with chloroform, transferred to methanol, and separated by HPLC on a Supelcosil LC-18 column with methanolwater as the mobile phase. The method was applied to several dairy cultures and cheese varieties. The amounts of glyoxal, methylglyoxal, and diacetyl in the cultures varied from 2 to 227, 0 to 7, and 1 to 11 ~tg/ml, respectively, depending on the species, strain, and culture medium.

Formation of Jumbo Yeast Cells by Introduction of Methylglyoxal Resistant Genes, Development of New Vector for Wild or Industrially Used Cells

Abstract: The two genes responsible for methylglyoxal (MG) resistance were cloned onto YEpl3 and designated as pYMG14 and pYGL7, respectively. The former was proved to code the gene for MG reductase, which converted MG to lactaldehyde. The latter was for glyoxalase I, which converted MG to S-lactoylglutathione in the presence of glutathione. Introduction of either one of these plasmids into yeast cells made the transformants not only resistant to high concentration of MG, but also 2 times bigger in size of diameter and 8 times in cubic content than control yeast cells. This is the first report that jumbo yeast cells are breeded by introduction of some genes. These jumbo yeast cells are not only interesting from the point of basic microbiology, but also industrially useful. The physiological properties of them are now underinvestigated.

Novel plasmid, novel bacterium transformed with said plasmid and enzymatic production of s-lactoylglutathione using said bacterium

Abstract: PURPOSE:To produce S-lactoylglutathione, by bringing Escherichia coli transduced with a structural gene of glyoxalase I derived from Pseudomonas putida into contact with a substrate containing methylglyoxal and glutathione. CONSTITUTION:Chromosome DNA of Pseudomonas putida IFO3738 is digested with restriction enzyme Sau3AI and connected to pBR322 digested with BamHI by T4 ligase to give pGI318. The plasmid is further treated with HindIII to give pGI423. Escherichia coli C600 strain is transduced with these plasmids to give C600 (pGI318) (FERM P-3638) and C600 (PGI423) (FERM P-3639). These strains are cultivated in a medium, the prepared cell or a treated material of the cell is brought into contact with a solution of a substrate containing methylglyoxal and glutathione to give S-lactoylglutathione.