Pflanzenphysiologisches Institut der Universität, Untere Karspüle 2, W-3400, Göttingen, Federal Republic of Germany.
Planta. 1992 Aug;188(1):62-9. doi: 10.1007/BF00198940.
The electrogenic Cl(-)-pump in the plasmalemma of the marine alga Acetabularia acetabulum (L.) Silva has been suggested to be an unusual type of ATPase (Gradmann, 1989, Methods Enzymol. 174, 490). For a biochemical treatment of this issue, a plasmalemma-rich membrane fraction from Acetabularia has been prepared by phase-partitioning. About 80% of the ATPase activity in this material is inhibited by vanadate (K I50=1-2 μM). The phosphohydrolytic properties of the corresponding enzyme were further investigated. Its primary substrate MgATP(2-) (K m about 270 μM). Compared with other plasmalemma ATPases, it has an extremely alkaline pH optimum (pH 8-8.5), a weak sensitivity to diethyl-stilbestrol and to N,N'-dicyclohexylcarbodiimide, a strong selectivity for Mg(2+) over alternative divalent cations, and a weak selectivity for ATP over other phosphohydrolytic substrates. It is insensitive to KCl at concentrations up to 200 mM. Both ATP(4-) and Mg2ATP inhibit the ATPase, satisfying a relationship for competitive inhibition by 2ATP(4-) (K IATP=1.56 mM) and noncompetitive inhibition by Mg2ATP (K IMg2ATP=1.35 mM). Since no transport experiments are reported in this study, the ion species (H(+) or Cl(-)) that is transferred by this ATPase is not identified.
海洋藻类石莼（Acetabularia acetabulum（L.）Silva）质膜中的电致 Cl(-)-泵被认为是一种不寻常的 ATP 酶类型（Gradmann，1989，Methods Enzymol. 174，490）。为了对此问题进行生化处理，通过相分离制备了富含质膜的石莼膜部分。该材料中约 80%的 ATP 酶活性被钒酸盐抑制（K I50=1-2 μM）。进一步研究了相应酶的磷酸水解性质。其主要底物是 MgATP(2-)（K m 约为 270 μM）。与其他质膜 ATP 酶相比，它具有极高的碱性 pH 最优值（pH 8-8.5），对二乙基己烯雌酚和 N,N'-二环己基碳二亚胺的敏感性较弱，对 Mg(2+)的选择性强于其他二价阳离子，对 ATP 的选择性弱于其他磷酸水解底物。在高达 200 mM 的 KCl 浓度下它不敏感。ATP(4-)和 Mg2ATP 均抑制 ATP 酶，满足 2ATP(4-)的竞争性抑制关系（K IATP=1.56 mM）和 Mg2ATP 的非竞争性抑制关系（K IMg2ATP=1.35 mM）。由于本研究中没有报道转运实验，因此无法确定该 ATP 酶转运的离子种类（H(+)或 Cl(-)）。
