HMG-CoA reductase activity in the microsomal fraction from human placenta in early and term pregnancy.
The activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) mevalonate: NADP oxidoreductase (CoA acylating; EC 1.1.1.34) in microsomes from early- and term-pregnancy placenta has been found to be 24 +/- 2 and 6 +/- 3 pmol/min per mg protein, respectively. Inactivation of the enzyme required the addition of ATP and Mg2+ and was dependent on the time of preincubation. Reactivation of the enzyme was also dependent on the incubation time and prevented by the presence of fluoride--a phosphoprotein phosphatase inhibitor. These data suggest that (despite a low activity) placental HMG-CoA reductase is covalently modulated via the phosphorylation-dephosphorylation system. The conversion of [14C]acetate and [3H]mevalonate into digitonin precipitable placental sterols indicates that the lower reductase activity in term, than in early, placental microsomes is accompanied by a less active conversion of [14C]acetate in this tissue.
D000085:Acetates / Q000378:metabolism; D005260:Female; D005865:Gestational Age; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D008798:Mevalonic Acid / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D013261:Sterols / Q000378:metabolism
D000085:Acetates; D013261:Sterols; D006903:Hydroxymethylglutaryl CoA Reductases; D008798:Mevalonic Acid