Protein glycation in Saccharomyces cerevisiae

Abstract

Methylglyoxal is the most important intracellular glycation agent, formed nonenzymatically from triose phosphates during glycolysis in eukaryotic cells. Methylglyoxal‐derived advanced glycation end‐products are involved in neurodegenerative disorders (Alzheimer's, Parkinson's and familial amyloidotic polyneurophathy) and in the clinical complications of diabetes. Research models for investigating protein glycation and its relationship to methylglyoxal metabolism are required to understand this process, its implications in cell biochemistry and their role in human diseases. We investigated methylglyoxal metabolism and protein glycation in Saccharomyces cerevisiae. Using a specific antibody against argpyrimidine, a marker of protein glycation by methylglyoxal, we found that yeast cells growing on d‐glucose (100 mm) present several glycated proteins at the stationary phase of growth. Intracellular methylglyoxal concentration, determined by a specific HPLC based assay, is directly related to argpyrimidine formation. Moreover, exposing nongrowing yeast cells to a higher d‐glucose concentration (250 mm) increases methylglyoxal formation rate and argpyrimidine modified proteins appear within 1 h. A kinetic model of methylglyoxal metabolism in yeast, comprising its nonenzymatic formation and enzymatic catabolism by the glutathione dependent glyoxalase pathway and aldose reductase, was used to probe the role of each system parameter on methylglyoxal steady‐state concentration. Sensitivity analysis of methylglyoxal metabolism and studies with gene deletion mutant yeast strains showed that the glyoxalase pathway and aldose reductase are equally important for preventing protein glycation in Saccharomyces cerevisiae.

Separation of monosaccharides hydrolyzed from glycoproteins without the need for derivatization

“…Yeast, in contrast to bacteria, are capable of higher forms of posttranslational modifications including glycosylation although 12 there are considerable differences observed between the glycan structures of yeast and mammalian origin. Yeast glycan structures are typically represented as high-mannose types, or as non-enzymatic glycation (glucose) products [30,31]. Accordingly, mannose, along with galactose and glucose, were observed as the major monosaccharides from this extract.…”

A glutathione-specific aldose reductase of Leishmania donovani and its potential implications for methylglyoxal detoxification pathway

“…Comparative studies on the importance of glyoxalase system with that of aldose reductase enzymes in yeast have shown that during oxidative stress conditions when the glutathione levels are low, aldose reductase converts methylglyoxal to acetol in NADPH dependent way (Ponces Freire et al, 2003;Gomes et al, 2005). Studies on the metabolism of 2-oxoaldehydes by glyoxalase and aldose reductase in human have shown that aldose reductase can reduce glutathione conjugates of methylglyoxal (Cagen and Pisano, 1979;Ramana et al, 2000).…”

“…Aldose reductase has broad substrate specificity. It has been shown that in yeast, during oxidative stress conditions, the glutathione levels are depleted and the glyoxalase enzymes are inactive, aldose reductase then detoxifies about 40% of the methylglyoxal in the cell (Ponces et al, 2003;Gomes et al, 2005). In liver, where the glutathione levels are high, glutathione dependent glyoxalase pathway is preferred over the NADPH dependent aldose reductase pathway.…”

Metilglioxal: uma toxina endógena?

“…166 Consistentemente, observou-se glicação de proteínas promovidas por metilglioxal em Saccharomyces. 167,168 Diferentemente de bactérias, a principal via de formação do metilglioxal em leveduras pode ser a decomposição química espontânea da di-hidroxicetona fosfato, pois não foi detectada atividade de metilglioxal sintetase. 164 Recentemente, análises do genoma de S. cerevisiae não revelaram sequências homólogas à da metilglioxal sintetase, o que corrobora trabalhos anteriores.…”