Placental estrogen synthetase (aromatase): evidence for phosphatase-dependent inactivation.
The acute regulation of estrogen synthetase (aromatase), the cytochrome P450 enzyme system responsible for estrogen production, is not well explored. We report here that aromatase, but not NADPH-cytochrome c (P450) reductase, activity from human term placental microsomes decreased when incubated in phosphate-free buffer at 37 degrees C. Aromatase activity was stabilized by phosphate buffer or by the phosphatase inhibitors tartaric acid or EDTA, but not NaF, in phosphate-free buffer. Alkaline phosphatase also inhibited aromatase in phosphate-free buffer relative to phosphate buffer, but the inactivation appears to be due primarily to proteolytic solubilization of NADPH-cytochrome c reductase from the microsomes by proteases within the alkaline phosphatase preparation. Based on these data, we suggest that the cytochrome P450 component of aromatase may be regulated acutely by phosphorylation-dependent processes.
Bellino
F L
FL
Dept. of Biological Sciences, SUNY/Buffalo 14260.
Holben
L
L
D001141:Aromatase / Q000378:metabolism*; D002021:Buffers; D004795:Enzyme Stability; D006801:Humans; D008861:Microsomes / Q000201:enzymology; D009245:NADH Dehydrogenase / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000502:physiology*; D010766:Phosphorylation; D011257:Pregnancy Proteins / Q000378:metabolism*
D002021:Buffers; D011257:Pregnancy Proteins; D001141:Aromatase; D009245:NADH Dehydrogenase; D010744:Phosphoric Monoester Hydrolases