Affinity labeling of cofactor-binding region of human placental estradiol 17 beta-dehydrogenase by periodate-oxidized NADP+ (o-NADP+).
Periodate-oxidized NADP+ (o-NADP+), an analogue of the cofactors, is a reversible inhibitor of estradiol 17 beta-dehydrogenase in human placenta. Mode of the inhibition by o-NADP+ appeared to be competitive type (Ki = 0.84 microM) against NAD+ and non-competitive type (Ki = 1.13 microM) against estradiol, respectively. Treatment of the estradiol 17 beta-dehydrogenase with o-NADP+ resulted in time-dependent loss of the enzyme activity. The inactivation exhibited pseudo-first order kinetics (t1/2 = 15 min) and was protected by NAD+ and NADP+. On the other hand, periodate-oxidized ATP inactivated slightly the estradiol 17 beta-dehydrogenase. These results indicate that the residue(s) of lysines is located near the cofactor-binding region of estradiol 17 beta-dehydrogenase of human placenta.
Inano
H
H
National Institute of Radiological Sciences, Chiba-shi, Japan.
Kurihara
S
S
D015067:17-Hydroxysteroid Dehydrogenases / Q000378:metabolism*; D000345:Affinity Labels; D001665:Binding Sites; D004960:Estradiol Dehydrogenases / Q000378:metabolism*; D006801:Humans; D008239:Lysine; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D010504:Periodic Acid; D010920:Placenta / Q000201:enzymology*
D000345:Affinity Labels; D010504:Periodic Acid; D009249:NADP; D015067:17-Hydroxysteroid Dehydrogenases; D004960:Estradiol Dehydrogenases; D008239:Lysine