Photochemical inactivation of human placental estradiol 17 beta-dehydrogenase in the presence of 2,3-butanedione.
Estradiol 17 beta-dehydrogenase of human placenta was rapidly inactivated by 2,3-butanedione under u.v. light, and no protection against the inactivation was observed in the presence of sodium azide. Under ordinary laboratory illumination, the inactivation was biphasically progressed in time-dependent and concentration-dependent manners, while a partial protection from the inactivation was indicated by sodium azide. These results suggest that the inactivation mechanism of the dehydrogenase by 2,3-butanedione under laboratory illumination is different from that under u.v. light. Therefore, the inactivation under laboratory illumination proceeded by a reaction with excited singlet molecular oxygen (1 delta g or 1 sigma +g states), and that under u.v. light was caused by a reaction of substrate with triplet sensitizer. In the presence of NADP+, the inactivation of the enzyme by 2,3-butanedione was markedly reduced. The maximum protection by NADP+ was about 80% of the initial enzyme activity. Amino acid analysis of the enzyme treated with 2,3-butanedione under laboratory illumination showed that the modified enzyme contained considerably less of the following amino acids than the native enzyme: histidine, arginine, threonine, methionine, tyrosine and leucine. In addition, other dicarbonyl reagents, 1,4-dibromo-2,3-butanedione, 1-phenyl-1,2-propanedione, phenylglyoxal, 16-oxoestrone, 1,2-cyclohexanedione, 2,4-pentanedione and glyoxal were found to decrease the dehydrogenase activity in various degree.
D015067:17-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors*; D000596:Amino Acids / Q000032:analysis; D002074:Butanones / Q000494:pharmacology*; D003931:Diacetyl / Q000494:pharmacology*; D004960:Estradiol Dehydrogenases / Q000037:antagonists & inhibitors*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010782:Photolysis; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D013329:Structure-Activity Relationship
D000596:Amino Acids; D002074:Butanones; D015067:17-Hydroxysteroid Dehydrogenases; D004960:Estradiol Dehydrogenases; D003931:Diacetyl