title: In vitro PGE2 synthesis by seminal vesicular microsomes: hysteretic behaviour in the presence of calcium ions.
abstract: When 4 mM Ca2+ is added gratuitiously in the reaction mixture synthesizing prostaglandin E2 (PGE2) from arachidonic acid and cofactors by membrane associated microsomal multienzyme system (MES) prepared from goat seminal vesicles, one observes an immediate lag in the production of PGE2. This Ca2+ induced lag is clearly due to the hysteretic response of MES promoted by Ca2+ ligand and not mediated through any effect of the divalent cation on the membrane, such as membrane phase separation. Preincubation studies indicated that the hysteretic response of MES is not due to Ca2+ ligand alone, but the substrate(s) also co-operate to modulate the enzyme system to demonstrate the characteristic nonlinear kinetics.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D015232:Dinoprostone; D006041:Goats; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010084:Oxidation-Reduction; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011458:Prostaglandins E / Q000096:biosynthesis*; D012669:Seminal Vesicles / Q000378:metabolism
chemical_list: D011458:Prostaglandins E; D011451:Prostaglandin-Endoperoxide Synthases; D009251:NADPH-Ferrihemoprotein Reductase; D015232:Dinoprostone; D002118:Calcium