RESUMO
Oviductal secretions include an ATPase (EC 3.6.1.3) that is transferred from the outer surface of the secretory cells to the surface of the ovulated oocyte. The enzyme has been purified and is a highly labile, very high molecular weight lipoprotein complex (greater than 4-10(6)). It consists of 47% protein and 53% lipid. Lipid composition is limited to phosphatidylcholine, phosphatidylethanolamine and sphingomyelin. The basic protein subunit has a molecular weight of 170 000. The enzyme exhibits many of the characteristics of ectoenzyme ATPase. The enzyme is Mg2+ or Ca2+ dependent; the Mg2+-ATPase has pH optima at 6.0 and 7.8 and the Ca2+-ATPase at 9.0. Substrate specificity is limited to ATP with lesser activity towards GTP, CTP, UPT and ADP. Km for ATP is 0.88 mM and the enzyme is inhibited at substrate concentrations greater than 3 mM ATP.
Assuntos
Adenosina Trifosfatases , Oviductos/enzimologia , Adenosina Trifosfatases/isolamento & purificação , Adenosina Trifosfatases/metabolismo , Animais , Cálcio/farmacologia , Galinhas , Ativação Enzimática , Feminino , Cinética , Lipoproteínas , Magnésio/farmacologia , Microscopia Eletrônica , Oviductos/ultraestrutura , Fosfolipídeos/análiseRESUMO
Avian oviductal fluids contain phosphorylating-dephosphorylating enzymes that might function in sperm-oocyte interactions. Phosphorprotein phosphatase and protein kinase have been purified 20-fold and 40-fold, respectively. The latter easily aggregates and is highly labile. Other properties are comparable to those of holoenzymes.