THE ROLE OF GLYOXALASE-I IN THE DETOXIFICATION OF METHYLGLYOXAL AND IN THE ACTIVATION OF THE KEFB K-COLI( EFFLUX SYSTEM IN ESCHERICHIA)

The glyoxalase I gene (gloA) of Escherichia coli has been cloned and u sed to create a null mutant. Cells overexpressing glyoxalase I exhibit enhanced tolerance of methylglyoxal (MG) and exhibit elevated rates o f detoxification, although the increase is not stoichiometric with the change in enzyme activity. Potassium efflux via KefB is also enhanced in the overexpressing strain. Analysis of the physiology of the mutan t has revealed that growth and viability are quite normal, unless the cell is challenged with MG either added exogenously or synthesized by the cells. The mutant strain has a low rate of detoxification of MG, a nd cells rapidly lose viability when exposed to this electrophile. Act ivation of KefB and KefC is diminished in the absence of functional gl yoxalase I. These data suggest that the glutathione-dependent glyoxala se I is the dominant detoxification pathway for MG in E. coli and that the product of glyoxalase I activity, S-lactoylglutathione, is the ac tivator of KefB and KefC.