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PubMedDate not supplied

[Quantitative determination of lactate, puruvate and methylglyoxa in their mixture].

A method is suggested for nonenzymic spectrophotometric determination of the content of lactic, pyruvic acids and methylglyoxal in their mixture without mutual interference. The determination may be conducted in the biological material after removing protein. 2,4 dinitrophenylhydrazine hydrochloride solution is added to the solution containing the above-mentioned components, then it is centrifuged. The content of lactate and pyruvate is determined in the supernatant fluid, that of methylglyoxal--in the sediment.

Aldehydes↗
PubMedDate not supplied

Studies on the interaction of fructose 1,6-P2 aldolase with methylglyoxal.

Reaction of rabbit muscle fructose 1,6-P2 aldolase with methylglyoxal results in a biphasic loss of activity. The kinetics of the initial rapid phase are first order with respect to the inhibitor. Dihydroxyacetone phosphate and fructose 1,6 bisphosphate afford complete protection whereas inorganic phosphate provides only a partial protection against inactivation. The treatment with methylglyoxal modifies the aldolase ability to bind D-Ga3P and DHAP. Loss of activity correlates with the modification of 1.7 arginine residues but data suggest that probably one of these arginine residues is essential. A likely role of this residue could be its interaction with the C1 negatively charged phosphate binding site of the enzyme.

Aldehydes↗
PubMed1981

Isolation of methylglyoxal synthase from goat liver.

An enzyme fraction which specifically catalyzes the formation of methylglyoxal from dihydroxyacetone phosphate has been isolated and partially purified from goat liver. The enzyme fraction appears to be substantially free from glyoxalase I, reduced glutathione, and triosephosphate isomerase. Approximately equimolar quantities of methylglyoxal and inorganic phosphate were obtained from dihydroxyacetone phosphate. Formation of methylglyoxal was confirmed by colorimetric and enzymatic estimations as well as by paper chromatography and its spectrum. Glyceraldehyde-3-phosphate, fructose 1,6-bisphosphate, dihydroxyacetone, and glyceraldehyde, failed to act as substrates. The enzyme is inhibited by some phosphorylated compounds and inorganic phosphates.

Animals↗
PubMed1981

Effect of methylglyoxal on rat liver lysosome-vacuolar apparatus.

Methylglyoxal (MeG) administration to rats doesn't cause any change in liver lysosome integrity; on the other hand, lysosome osmotic fragility appears highly increased at short times after the treatment. Concomitantly, a significant decrease of the residual latent activity of acid phosphatase (RLA = activity which cannot be unmasked by extensive hypo-osmotic shock) occurs. Cycloheximide (CHM), when administered shortly before MeG, prevents both the changes in RLA and in osmotic fragility. These results point to a big stimulation of autophagy in rat liver by MeG.

Acid Phosphatase↗
PubMed1980

Decarboxylated S-adenosylmethionine in mammalian cells.

The content of decarboxylated S-adenosylmethionine in rat tissues was found to be of the order of 0.9 to 2.5 nmol/g wet weight, about 2 to 4% of the content of S-adenosylmethionine. Three methods were used for determinations: separation by high pressure liquid chromatography followed by quantitation using UV absorbance, separation by paper electrophoresis after labeling with radioactive methionine to get the ratio of S-adenosylmethionine to decarboxylated S-adenosylmethionine, and separation by electrophoresis followed by elution and assay by an isotope dilution technique using spermidine synthase. The three methods gave comparable results, although the labeling with methionine appeared to slightly overestimate levels in the liver. Hepatic decarboxylated S-adenosylmethionine content was reduced by more than 90% for at least 8 h by treatment with methylglyoxal bis(guanylhydrazone), a potent reversible inhibitor of S-adenosylmethionine decarboxylase, but had returned to control levels by 24 h. The related irreversible inhibitor, 1,1'-[(methylethanediylidene)-dinitrilo]bis(3-aminoguanidine), reduced levels slightly less to about 20% of control, but maintained them at this value for 2 days.

Animals↗
PubMed1995

In vitro biocompatibility of a heat-sterilized, low-toxic, and less acidic fluid for peritoneal dialysis.

OBJECTIVE: The aim of this study was to investigate a peritoneal dialysis (PD) fluid (PD-Bio), produced with the intention of reducing the amount of glucose degradation products and to increase the final pH. The heat sterilization of the fluid was performed with the glucose separated from the electrolytes. After sterilization the two solutions were combined. METHODS: The in vitro biocompatibility of PD-Bio was measured as the inhibition of cell growth of a cultured fibroblast cell line and as the stimulated release of interleukin-1 beta from cultured human mononuclear cells. The glucose degradation products were measured as UV absorbance at 228 nm or 284 nm and the concentration of aldehydes was estimated with high-performance liquid chromatography and gas chromatography. RESULTS: Our results demonstrate that in comparison to conventional PD fluids the pH of PD-Bio was increased, to about 6.5. Due to less contaminating glucose degradation products in PD-Bio, basal cytotoxicity was significantly decreased for both 1.5% and 4% glucose-containing fluids, and the stimulated release of interleukin-1 beta was normalized compared to sterile filtered controls with the same pH. UV absorbance measured at 228 nm was decreased, whereas the absorbance at 284 nm was equal to that of a conventional fluid. In PD-Bio the concentrations of formaldehyde, acetaldehyde, methylglyoxal, and 2-furaldehyde were found to be below the detection limit, whereas glyoxal was present in the same and 5-hydroxymethylfurfural (5-HMF) in higher concentrations than in conventionally produced PD fluid. CONCLUSIONS: The results demonstrate that it is possible to improve biocompatibility of PD fluids by simply changing the way the fluid is produced.

Acetaldehyde↗
PubMed1994

Receptor-mediated endocytic uptake of methylglyoxal-modified serum albumin. Competition with advanced glycation end product-modified serum albumin at the advanced glycation end product receptor.

Methylglyoxal binds and irreversibly modifies arginine and lysine residues in bovine serum albumin (BSA) under physiological conditions, producing a protein with an increased net negative charge at physiological pH. At 4 degrees C, methylglyoxal-modified BSA (MG-BSA) was bound by cell surface receptors on murine P388D1 macrophages. The apparent dissociation constant KD value was 435 +/- 2 nM, and there were 8.89 +/- 0.02 x 10(5) receptors/cell (n = 6), compare with an apparent KD value of 263 +/- 52 nM and 10.17 +/- 0.93 x 10(5) receptors/cell (n = 11) for advanced glycation end product-modified BSA (AGE-BSA). AGE-BSA competed with MG-BSA for binding to a common receptor; however, a component of AGE-BSA receptor binding could not be displaced by MG-BSA, and a component of MG-BSA receptor binding could not be displaced by AGE-BSA, suggesting that there are binding sites for both AGE-BSA and MG-BSA, competitive and noncompetitive, to MG-BSA and AGE-BSA on P388D1 cells at 4 degrees C. At 37 degrees C, receptor binding of AGE-BSA and MG-BSA was followed by endocytosis and lysosomal degradation of the modified protein. Methylglyoxal-modified proteins are ligands for the AGE receptor, and their formation and metabolism may be linked to the development of diabetic complications.

Amino Acids↗
PubMed1994

Binding and modification of proteins by methylglyoxal under physiological conditions. A kinetic and mechanistic study with N alpha-acetylarginine, N alpha-acetylcysteine, and N alpha-acetyllysine, and bovine serum albumin.

The physiological alpha-oxoaldehyde methylglyoxal binds and modifies arginine, lysine, and cysteine residues in proteins. The kinetics and mechanism of these reactions were investigated with N alpha-acetylamino acids and bovine serum albumin at pH 7.4 and 37 degrees C. The reaction of methylglyoxal with N alpha-acetylarginine involved the initial reversible formation of glycosylamine and 4,5-dihydroxy-5-methylimidazolidine derivatives, with further slow irreversible conversion to an imidazolone, N alpha-acetyl-N delta- (5-methyl-4-imidazolon-2-yl)ornithine. The imidazolone was fluorescent with an excitation lambda max value of 320 nm and an emission lambda max value of 398 nm. Methylglyoxal reacted reversibly with N alpha-acetyllysine to form glycosylamine and bisglycosylamine derivatives. Further reaction of these glycosylamines occurred to form brown, fluorescent oligomers that were not characterized. Methylglyoxal reacted rapidly and reversibly with N alpha-acetylcysteine to form the hemithioacetal adduct. The reaction of methylglyoxal with bovine serum albumin (BSA) at pH 7.4 and 37 degrees C involved the reversible and irreversible formation of methylglyoxal-BSA adducts. Irreversible modification of BSA occurred mainly on arginine residues to form imidazolone. The formation of methylglyoxal-modified proteins involves glycoxidation leading to advanced glycation end product-like fluorescence. It is expected to be increased in diabetes mellitus and may be linked to the development of diabetic complications.

Acetylcysteine↗
PubMed1993

[Submolecular theory of cancer. In memoriam Albert Szent-Györgyi].

The author surveys the way leading to the electronic theory of cancer and analyses the role of methylglyoxal and glyoxalases. Based on the comparison of experimental data with the theory it can be concluded that (i) data being at disposal are not convincing enough either to verify or to confute the theory; (ii) compounds having function to influence the glyoxalase system can, however, be considered as tumour-selective anticancer agents.

Animals↗
PubMedDate not supplied

Kinetics of alpha-dicarbonyls reduction by L-glycol dehydrogenase (NAD+) from Enterobacter aerogenes.

L-glycol dehydrogenase from Enterobacter aerogenes shows a high affinity by NADH (Ks = 2-4 microM; Km = 4.3-9.7 microM), which indicates that it must operate in vivo saturated with this coenzyme. Michaelis and dissociation constants for the reduction of the carbonyl substrates assayed (diacetyl, 2,3-pentanedione, methylglyoxal and ethyl pyruvate) are similar to those reported for other diacetyl reducing enzymes. The kinetic mechanism followed by these reactions has also been studied. Our results prove that the reduction of diacetyl and ethyl pyruvate takes place via an Ordered Bi-Bi system with the coenzyme as the leading substrate. Methylglyoxal and 2,3-pentanedione are reduced by the same mechanism or by a Theorell-Chance one.

Acetone↗
PubMed1995

[Role of glyoxalases and methylglyoxal in cell proliferation and differentiation].

The glyoxalase system catalyses the conversion of methylglyoxal (and other 2-ketoaldehydes) to D-lactic acid via the intermediate S-D-lactoylglutathione. It comprises two enzymes, glyoxalases I and glyoxalases II, and catalytic amount to reduced glutathione. Methylglyoxal inhibits cell growth, while the glyoxalase system by breaking down methylglyoxal may act as a promoter of cell growth. Inhibitors of glyoxalases may serve as possible therapeutic agents against cancer by virtue of their ability to elevate the level of methylglyoxal in the body.

Animals↗
PubMedDate not supplied

Are aldehydes in heat-sterilized peritoneal dialysis fluids toxic in vitro?

OBJECTIVE: Chemical analysis of several brands of peritoneal dialysis fluids (PD fluids) has revealed the presence of 2-furaldehyde, 5-HMF (5-hydroxymethylfuraldehyde), acetaldehyde, formaldehyde, glyoxal, and methylglyoxal. The aim of this study was to investigate if the in vitro side effects caused by glucose degradation products, mainly formed during heat sterilization, are due to any of these recently identified aldehydes. DESIGN: Cell growth media or sterile filtered PD fluids were spiked with different concentrations of thealdehydes. MEASUREMENTS: In vitro side effects were determined as the inhibition of cell growth of cultured mouse fibroblasts or stimulated superoxide radical release from human peritoneal cells. RESULTS: Our results demonstrate that the occurrences of 2-furaldehyde, 5-HMF, acetaldehyde, formaldehyde, glyoxal, or methylglyoxal in heat-sterilized PD fluids are probably not the direct cause of in vitro side effects. In order to induce the same magnitude of cell growth inhibition as the heat-sterilized PD fluids, the concentrations of 2-furaldehyde, glyoxal, and 5-HMF had to be 50 to 350 times higher than those quantified in the PD fluids. The concentrations of acetaldehyde, formaldehyde, and methylglyoxal observed in the heat-sterilized PD fluids were closer to the cytotoxic concentrations although still 3 to 7 times lower. CONCLUSION: Since none of these aldehydes caused in vitro toxicity at the tested concentrations, the toxicity found in PD fluids is likely to be due to another glucose degradation product, not yet identified. However, it is possible that these aldehydes may still have adverse effects for patients on peritoneal dialysis.

Acetaldehyde↗
PubMedDate not supplied

[Splitting of fructose diphosphate by muscle and tumor homogenates].

Effect of MgCl2 and ATP on the elevation in lactate, pyruvate and methylglyoxale content was studied on incubation of fructosediphosphate with muscle and tumor homogenates. Muscle homogenate accumulated lactate, pyruvate and methyglyoxale more intensively as compared with tumor homogenate. Pyruvate was formed only in presence of MgCl2 and ATP, although it did not practically affect the elevation of lactate in muscle homogenate. The data obtained suggest that tumor homogenate does not contain the enzymatic system involved in methylglyoxale formation.

Adenosine Triphosphate↗
PubMed1996

Force, development, and neoplasia: development from another perspective as illustrated through a study of in vitro plant development from neoplasm.

Differentiation from the neoplastic state can be a dynamic adaptation to the localized stress of increasing cohesive forces in tissue. Repulsive forces, occurring within and between cells, are seen as leading to de-differentiation into the neoplastic state or neoplasm. During early development, especially where and when mitosis occurs frequently, cohesive and repulsive forces may necessarily coexist in oscillating degrees. Correspondingly, cohesive-force and repulsive-force generating metabolites may co-exist in oscillating concentrations. Cancer or neoplasia occurs, according A. Szent-Gyorgyi, when cohesiveness breaks down locally, probably thru the conversion of methylglyoxal into lactic acid. Cancer may also occur due to the accumulation of such putatively, repulsion-generating factors as lactic acid. Plant tumors in vitro respond adaptively to cohesion-generating chemicals, such as ascorbic acid and methylglyoxal, by generating buds, embryos, and plantlets.

Adaptation, Physiological↗