骨骼肌中的D-肌醇1,4,5-三磷酸磷酸酶
D-myo-inositol 1,4,5-trisphosphate phosphatase in skeletal muscle.
作者信息
Milani D, Volpe P, Pozzan T
机构信息
Centro di Studio delle Biomembrane del CNR, Università di Padova, Italy.
出版信息
Biochem J. 1988 Sep 1;254(2):525-9. doi: 10.1042/bj2540525.
The presence and subcellular distribution of D-myo-inositol 1,4,5-trisphosphate phosphatase (InsP3ase) in rabbit fast-twitch skeletal muscle were investigated. A specific InsP3ase was found in both sarcotubular-membrane and soluble fractions. Membrane-bound InsP3ase accounted for 60-65% of total activity. The InsP3ase was detected both on the surface membranes and on the InsP3-sensitive intracellular Ca2+ store, i.e. the sarcoplasmic reticulum. The Km for inositol 1,4,5-trisphosphate (InsP3) ranged between 15 and 18 microM, and the highest Vmax. (19.6 nmol of InsP3 hydrolysed/min per mg of protein) was measured in a membrane fraction enriched in transverse tubules. Several known inhibitors of InsP3ase, e.g. 2,3-bisphosphoglycerate, CdCl2 and EDTA, were active on skeletal-muscle InsP3ase. Total InsP3ase activity of both rabbit and frog skeletal muscle was comparable with that of rabbit brain, liver and main pulmonary artery (smooth muscle). The present results are consistent with the hypothesis that InsP3 plays a role in excitation-contraction coupling in skeletal muscle [Volpe, Salviati, Di Virgilio & Pozzan (1985) Nature (London) 316, 347-349].
研究了D-肌醇1,4,5-三磷酸磷酸酶（InsP3ase）在兔快肌骨骼肌中的存在及亚细胞分布。在肌管膜和可溶性部分均发现了一种特异性InsP3ase。膜结合型InsP3ase占总活性的60 - 65%。在表面膜和InsP3敏感的细胞内钙库即肌浆网上均检测到了InsP3ase。肌醇1,4,5-三磷酸（InsP3）的米氏常数（Km）在15至18微摩尔之间，在富含横管的膜部分测得最高的最大反应速度（Vmax）（每毫克蛋白质每分钟水解19.6纳摩尔InsP3）。几种已知的InsP3ase抑制剂，如2,3-二磷酸甘油酸、CdCl2和EDTA，对骨骼肌InsP3ase有活性。兔和蛙骨骼肌的总InsP3ase活性与兔脑、肝和主肺动脉（平滑肌）的相当。目前的结果与InsP3在骨骼肌兴奋-收缩偶联中起作用这一假说一致[沃尔佩、萨尔维亚蒂、迪·维尔吉利奥和波赞（1985年）《自然》（伦敦）316, 347 - 349]。
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