Anti-glycation defences in yeast.

Saccharomyces cerevisiae is an outstanding cellular model for metabolic studies in glycation. Due to its high glycolytic activity, it produces methylglyoxal, a highly reactive intracellular glycation agent, at a rate of approx. 0.1% of the glycolytic flux. We investigated methylglyoxal metabolism in Saccharomyces cerevisiae cells, using haploid null mutants. Growth studies showed that the most sensitive strains to 2-oxoaldehydes were the null mutants for GSH1 and GLO1, coding for glutathione synthase I and glyoxalase I respectively. The GRE3 null mutant, lacking aldose reductase activity, is as sensitive as the control strain. Kinetic modelling and computer simulation of this type of experiment were also performed, and we concluded that the most important parameters for controlling the intracellular concentration of methylglyoxal are the activity of glyoxalase I and the GSH concentration. Moreover, our model predicts an intracellular steady-state concentration of methylglyoxal of approx. 2 microM. Our results show that the glyoxalase pathway is the main detoxification pathway for 2-oxoaldehydes in yeast, and is likely to be the key enzymatic anti-glycation agent in these cells.