Alves E W, Ferreira C T, Teixeira-Ferreira A
Departamento de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Brasil.
Braz J Med Biol Res. 1992;25(11):1113-6.
The Ca2+ release mechanism that triggers muscle contraction is still not completely understood. We compared Ca2+ accumulation and acetyl phosphate hydrolysis by the Ca(2+)-ATPases present in the longitudinal and junctional membrane of the sarcoplasmic reticulum of rabbit skeletal muscle and found that Ca(2+)-ATPase is more sensitive to ADP inhibition when the enzyme is located on the junctional membrane than when the enzyme is located on the longitudinal membrane (K0.5 = 144 microM for the junctional enzyme vs K0.5 = 415 microM for the longitudinal enzyme). When the enzyme was solubilized in non-ionic detergent (2% v/v Triton X-100) and tested again using 2 mM AcP as substrate, the difference in ADP sensitivity observed with native preparations disappeared. We conclude that the enzyme is regulated differently depending on its localization on the membrane of the sarcoplasmic reticulum.
触发肌肉收缩的钙离子释放机制仍未被完全理解。我们比较了兔骨骼肌肌浆网纵向膜和连接膜中存在的钙离子 - ATP酶的钙离子积累和乙酰磷酸水解情况，发现当该酶位于连接膜上时比位于纵向膜上时对ADP抑制更敏感（连接膜酶的K0.5 = 144微摩尔，纵向膜酶的K0.5 = 415微摩尔）。当该酶用非离子去污剂（2% v/v Triton X - 100）溶解并再次以2毫摩尔乙酰磷酸作为底物进行测试时，天然制剂中观察到的ADP敏感性差异消失了。我们得出结论，该酶根据其在肌浆网膜上的定位而受到不同的调节。
