Placental estrogen synthetase (aromatase): evidence for phosphatase-dependent inactivation |
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Authors: | F L Bellino L Holben |
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Institution: | Dept. of Biological Sciences, SUNY/Buffalo 14260. |
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Abstract: | 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. |
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