Dissociation between Ca2+-ATPase and alkaline phosphatase activities in plasma membranes of rat duodenum.
Dissociation between Ca2+-ATPase and alkaline phosphatase activities in plasma membranes of rat duodenum.
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大鼠十二指肠质膜中Ca2+-ATP酶和碱性磷酸酶活性的解离。
DOI：
10.1016/0005-2736(80)90198-4
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
C. van Os
中科院分区：
文献类型：
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作者：
W. Ghijsen;M. D. de Jong;C. van Os
在大鼠十二指肠上皮细胞刷状缘和基底侧质膜上存在Ca 2+-ATP酶活性，其活性位点对Ca 2+具有高亲和力（Ghijsen，WEJM和货车Os，CH（1979）Nature 279，802-803）。由于两种质膜都含有碱性磷酸酶（EC 3.1。3.1），也可被Ca 2+激活，研究了Ca 2+诱导ATP水解的底物特异性，以确定碱性磷酸酶和Ca 2+-ATP酶是否为两种不同的酶。在基底外侧碎片中，当Ca 2+浓度低于25 μM时，Ca 2+依赖的ATP水解速率大于ADP、AMP和对硝基苯磷酸。在0.2mMCa2+时，ATP、ADP、AMP和对硝基苯磷酸水解速率无显著差异。在刷状缘碎片中，低Ca 2+时ATP、ADP和AMP的水解速率相同，但在0.2mMCa2+时，Ca 2+诱导的ADP和AMP的水解速率大于ATP和对硝基苯磷酸。碱性磷酸酶在刷状缘和基底外侧膜被抑制75%后，加入2.5 mM茶碱。Ca 2+刺激的ATP水解在1 μM Ca 2+浓度下对基底外侧碎片中的茶碱不敏感，而在刷状缘碎片中的ATP水解被完全抑制。在0.2mMCa2+时，Ca 2+诱导的基底膜和刷状缘膜ATP水解对茶碱敏感。寡霉素和叠氮化合物对Ca 2+刺激的ATP水解无影响，无论是在低浓度还是高浓度Ca 2+条件下。当Ca 2+浓度为5 μM时，氯丙嗪可完全抑制Ca 2+刺激的基底外侧碎片中的ATP水解，而对刷状缘碎片无影响。结果表明：（i）Ca 2+-ATPase和碱性磷酸酶是两种不同的酶，（ii）高亲和力的Ca 2+-ATPase只存在于基底外侧质膜，（iii）存在于十二指肠上皮两侧的碱性磷酸酶活性受低浓度Ca 2+的轻微刺激，但这种Ca 2+诱导的活性可被茶碱抑制，对ATP、ADP或AMP无特异性。
Abstract The presence of Ca 2+-ATPase activities with high-affinity sites for Ca 2+ in brush border as well as basolateral plasma membranes of rat duodenal epithelium has been reported previously (Ghijsen, WEJM and van Os, CH (1979) Nature 279, 802–803). Since both plasma membranes contain alkaline phosphatase (EC 3.1. 3.1), which also can be stimulated by Ca 2+, the substrate specificity of Ca 2+-induced ATP-hydrolysis has been studied to determine whether or not alkaline phosphatase and Ca 2+-ATPase are two distinct enzymes. In basolateral fragments, the rate of Ca 2+-dependent ATP-hydrolysis was greater than that of ADP, AMP and p-nitrophenylphosphate at Ca 2+ concentrations below 25 μM. At 0.2 mM Ca 2+ the rates of ATP, ADP, AMP and p-nitrophenylphosphate hydrolysis were not significantly different. In brush border fragments the rates of ATP, ADP and AMP hydrolysis were identical at low Ca 2+, but at 0.2 mM Ca 2+, Ca 2+-induced hydrolysis of ADP and AMP was greater than either ATP or p-nitrophenylphosphate. Alkaline phosphatase in brush border and basolateral membranes was inhibited by 75% after addition of 2.5 mM theophylline. Ca 2+-stimulated ATP hydrolysis at 1 μM Ca 2+ was not sensitive to theophylline in basolateral fragments while the same activity in brush border fragments was totally inhibited. At 0.2 mM Ca 2+, Ca 2+-induced ATP hydrolysis in both basolateral and brush border membranes was sensitive to theophylline. Oligomycin and azide had no effect on Ca 2+-stimulated ATP hydrolysis, either at low or at high Ca 2+ concentrations. Chlorpromazine fully inhibited Ca 2+-stimulated ATP hydrolysis in basolateral fragments at 5 μM Ca 2+, while it had no effect in brush border fragments. From these results we conclude that,(i) Ca 2+-ATPase and alkaline phosphatase are two distinct enzymes,(ii) high-affinity Ca 2+-ATPase is exclusively located in basolateral plasma membranes,(iii) alkaline phosphatase activity, present on both sides of duodenal epithelium, is stimulated slightly by low Ca 2+ concentrations, but this Ca 2+-induced activity is inhibited by theophylline and shows no specificity with respect to ATP, ADP or AMP.