A DNA fragment carrying a part of the structural gene for yeast (Saccharomyces cerevisiae) glyoxalase I was cloned from a lambda gt11 expression library using anti-glyoxalase IIgG as a probe. By Northern blotting analysis, the amount of glyoxalase I mRNA was found to increase in yeast cells containing plasmids carrying the GAC gene, which is a positive regulator for yeast glyoxalase I activity. This suggests that the GAC gene product may accelerate the transcription of glyoxalase I gene or may have some positive effects on the accumulation of glyoxalase I mRNA in yeast cells.