肌浆网Mg2+依赖的ATP酶的动力学特性

Kinetic characterization of Mg2+-dependent ATPase of sarcoplasmic reticulum.

作者信息

Perret M L, Vianna A L

出版信息

An Acad Bras Cienc. 1981 Mar;53(1):173-81.

Abstract

Kinetic properties of Mg2+-dependent ATPase activity (basic activity) of sarcoplasmic reticulum vesicles are studied in silver-treated preparations. The treated vesicles are shown to have no Mg2+ + Ca2+-dependent ATPase activity (extra activity) and a basic specific activity which is similar to that of untreated vesicles. The basic ATPase activity can be stimulated by different divalent cations. The relative effectiveness of activation is: Ca greater than Mg greater than or equal to MN greater than Cd greater than or equal to Co greater than Zn greater than Ni = Sr. The metal-ATP complex (MgATP or CaATP) is the true substrate of basic ATPase activity while the free ATP is a competitive inhibitor. The Km's found for MgATP and CaATP are respectively 0.32 mM and 0.41 mM. Ki for free ATP is in the range of 2 to 3 mM. The free divalent cations do not affect the ATPase activity. Both MgITP and CaITP are hydrolysed by the enzyme. The Km's for these complexes are respectively 0.67 and 0.73 mM. The Km for the substrate decreases when the pH of the medium increases from 5.5 to 8.5.

摘要

在经银处理的制剂中研究了肌浆网囊泡的Mg2+依赖性ATP酶活性（基础活性）的动力学特性。结果表明，处理后的囊泡没有Mg2+ + Ca2+依赖性ATP酶活性（额外活性），且基础比活性与未处理的囊泡相似。基础ATP酶活性可被不同的二价阳离子刺激。激活的相对有效性为：Ca大于Mg大于或等于Mn大于Cd大于或等于Co大于Zn大于Ni = Sr。金属 - ATP复合物（MgATP或CaATP）是基础ATP酶活性的真正底物，而游离ATP是竞争性抑制剂。MgATP和CaATP的Km值分别为0.32 mM和0.41 mM。游离ATP的Ki在2至3 mM范围内。游离二价阳离子不影响ATP酶活性。MgITP和CaITP均可被该酶水解。这些复合物的Km值分别为0.67和0.73 mM。当培养基的pH从5.5增加到8.5时，底物的Km值降低。