Watters C D
Biochem J. 1984 Nov 15;224(1):39-45. doi: 10.1042/bj2240039.
A membrane fraction isolated from lactating murine mammary tissue and enriched for the Golgi membrane marker enzyme galactosyltransferase exhibited Ca2+-stimulated ATPase activity (Ca-ATPase) in 20 microM-free Mg2+ and 10 microM-MgATP, with an apparent Km for Ca2+ of 0.8 microM. Exogenous calmodulin did not enhance Ca2+ stimulation, nor could Ca-ATPase activities be detected in millimolar total Mg2+ and ATP. When assayed with micromolar Mg2+ and MgATP the Ca-ATPases of skeletal-muscle sarcoplasmic reticulum and of calmodulin-enriched red blood cell plasma membranes were half-maximally activated by 0.1 microM- and 0.6 microM-Ca2+ respectively. All three Ca-ATPases were inhibited by similar micromolar concentrations of trifluoperazine, but the Golgi activity was unaffected by quercetin in concentrations which completely inhibited both the sarcoplasmic-reticulum and red-blood-cell enzymes. The results are consistent with the hypothesis that the high-affinity Ca-ATPase is responsible for the ATP-dependent Ca2+ transport exhibited by Golgi-enriched vesicles derived from lactating mammary gland [Neville, Selker, Semple & Watters (1981) J. Membr. Biol. 61, 97-105; West (1981) Biochim. Biophys. Acta 673, 374-386].
从泌乳期小鼠乳腺组织分离得到的富含高尔基体膜标记酶半乳糖基转移酶的膜组分,在20微摩尔无镁离子和10微摩尔镁 - 三磷酸腺苷(MgATP)存在的情况下,表现出钙离子刺激的三磷酸腺苷酶活性(钙 - 三磷酸腺苷酶),钙离子的表观米氏常数(Km)为0.8微摩尔。外源性钙调蛋白不会增强钙离子刺激,在毫摩尔浓度的总镁离子和三磷酸腺苷中也检测不到钙 - 三磷酸腺苷酶活性。当用微摩尔浓度的镁离子和MgATP进行测定时,骨骼肌肌浆网和富含钙调蛋白的红细胞质膜的钙 - 三磷酸腺苷酶分别被0.1微摩尔和0.6微摩尔的钙离子激活到最大活性的一半。所有这三种钙 - 三磷酸腺苷酶都受到类似微摩尔浓度氟哌嗪的抑制,但高尔基体的活性不受槲皮素的影响,而相同浓度的槲皮素能完全抑制肌浆网和红细胞的酶活性。这些结果与以下假设一致:高亲和力的钙 - 三磷酸腺苷酶负责泌乳期乳腺来源的富含高尔基体的囊泡所表现出的依赖三磷酸腺苷的钙离子转运[内维尔、塞尔克、森普尔和沃特斯(1981年)《膜生物学杂志》61卷,97 - 105页;韦斯特(1981年)《生物化学与生物物理学报》673卷,374 - 386页]。