1.NounEither of a pair of related thiol-dependent enzymes: glyoxalase І, which catalyse the isomerisation of the spontaneously formed hemithioacetal adduct between GSH and 2-oxoaldehydes (such as methylglyoxal) into S-2-hydroxyacylglutathione; and glyoxalase ІІ, which hydrolyses these thiolesters.