MOLECULAR CHARACTERIZATION OF GLYOXALASE-II FROM ARABIDOPSIS-THALIANA

Glyoxalase II is part of the glutathione-dependent glyoxalase detoxifi cation system. In addition to its role in the detoxification of cytoto xic 2-oxo-aldehydes, specifically methylglyoxal, it has been suggested that the glyoxalase system may also play a role in controlling cell d ifferentiation and proliferation. During the analysis of a T-DNA-tagge d mutant of Arabidopsis we identified the gene for a glyoxalase II iso zyme (GLY1) that appears to be mitochondrially localized. The cDNA enc oding a glyoxalase II cytoplasmic isozyme (GLY2) was also isolated and characterized. Southern blot and sequence analyses indicate that glyo xalase II proteins are encoded by at least two multigene families in A rabidopsis. Escherichia coli cells expressing either GLY1 or GLY2 exhi bit increased glyoxalase II activity, confirming that they do, in fact , encode glyoxalase II proteins. Northern analysis shows that the two genes are differentially expressed. Transcripts for the mitochondrial isozyme are most abundant in roots, while those for the cytoplasmic is ozyme are highest in flower buds. The identification of glyoxalase II isozymes that are differentially expressed suggests that they may play different roles in the cell.