Bingham E W, McGranaghan M B, Wickham E D, Leung C T, Farrell H M
US Department of Agriculture, ARS Eastern Regional Research Center, Philadelphia, PA 19118.
J Dairy Sci. 1993 Feb;76(2):393-400. doi: 10.3168/jds.S0022-0302(93)77358-0.
The [Ca2+ + Mg2+]-ATPase activity of bovine lactating mammary gland is associated with membranes. This study compares the ATPase activity in microsomal membranes to that of the Golgi apparatus. The enzyme activity in both fractions hydrolyzed Ca(2+)-ATP and Mg(2+)-ATP. The ATPase activities were inhibited by p-chloromercuribenzoate, indicating the involvement of a sulfhydryl group for activity. Although calmodulin had no effect on the ATPase activities of the two fractions, calmodulin antagonists (chlorpromazine, fluphenazine, and trifluoperazine) were inhibitory. Strong inhibitors of the ATPase activities were vanadate, dicyclohexyl-carbodiimide, La3+, and Zn2+. There were some differences in the activities from two membrane fractions. Although both fractions could hydrolyze all of the triphosphonucleotides, cytidine-5'-triphosphate and uridine-5'-triphosphate were poor substrates for the Golgi enzyme. Detergents diminished the activity of the microsomal enzyme to a much greater extent than the ATPase of the Golgi apparatus. Thus, the intact membrane may be more critical to microsomal activity. The role of these enzymes in Ca2+ accumulation in milk is discussed.
牛泌乳乳腺的[Ca2+ + Mg2+]-ATP酶活性与膜相关。本研究比较了微粒体膜和高尔基体中的ATP酶活性。两个组分中的酶活性均可水解Ca(2+)-ATP和Mg(2+)-ATP。对氯汞苯甲酸抑制了ATP酶活性，表明巯基参与了该活性。尽管钙调蛋白对两个组分的ATP酶活性均无影响，但钙调蛋白拮抗剂（氯丙嗪、氟奋乃静和三氟拉嗪）具有抑制作用。ATP酶活性的强抑制剂有钒酸盐、二环己基碳二亚胺、La3+和Zn2+。两个膜组分的活性存在一些差异。尽管两个组分均可水解所有三磷酸核苷酸，但胞苷-5'-三磷酸和尿苷-5'-三磷酸是高尔基体酶的较差底物。去污剂对微粒体酶活性的降低程度远大于对高尔基体ATP酶活性的降低程度。因此，完整的膜对微粒体活性可能更为关键。文中讨论了这些酶在乳汁中Ca2+积累中的作用。
