Methylglyoxal concentration and glyoxalase activities in the human lens

The activities of glyoxalase I and glyoxalase II and the concentration of methylglyoxal were determined in 26 human lenses. The activity of glyoxalase I (mean +/- S.D.) was 15.62 +/- 3.90 U (g wet weight)-1 and the activity of glyoxalase II was 0.189 +/- 0.087 U (g wet weight)-1 (n = 26). The concentration of methylglyoxal of the human lenses was 1.78 +/- 0.84 nmol (g wet weight)-1 (n = 26). There was a significant negative correlation of both the activity of glyoxalase I and the activity of glyoxalase II with subject age but no correlation of methylglyoxal concentration with subject age. The concentration of methylglyoxal in the lenses was approximately 20-fold higher than in blood samples from normal human subjects. Given the previously reported decrease in the concentration of reduced glutathione in the human lens with age, there is expected to be a marked decrease in in situ activity of glyoxalase I and concomitant susceptibility of human lens proteins to modification by methylglyoxal with age. The metabolism of methylglyoxal and the formation of methylglyoxal-modified proteins may be linked to the development of senile and diabetic cataract.