COMPARISON OF THE MYOSIN AND ACTOMYOSIN ATPASE MECHANISMS OF THE 4 TYPES OF VERTEBRATE MUSCLES
COMPARISON OF THE MYOSIN AND ACTOMYOSIN ATPASE MECHANISMS OF THE 4 TYPES OF VERTEBRATE MUSCLES
复制标题
DOI：
10.1016/0022-2836(80)90050-9
复制
发表时间：
1980-01-01
影响因子：
5.6
通讯作者：
TAYLOR, EW
中科院分区：
文献类型：
--
作者：
MARSTON, SB;TAYLOR, EW
研究了肌球蛋白和动肌球蛋白对脊椎动物4种主要肌群：快白色肌（背阔肌后部）、慢红色肌（背阔肌前部）、贲门肌和光滑肌（肌胃）的ATP水解机制。所有类别的肌肉的动力学行为是一致的，与以前开发的方案为兔快白色肌肉，但定量差异，观察到的水解周期中的一些步骤的速率常数。肌球蛋白亚片段-1的水解步骤的速率在横纹肌中相似，在平滑肌中小2 - 3倍。在导致肌球蛋白产物中间体形成的途径中发生酶的两种异构化。ATP对acto S-1 [肌细胞素亚片段1]的解离速率在慢速肌肉中较慢，在低温下观察到最大速率。在低浓度肌动蛋白时，S-1产物中间体与肌动蛋白的结合速率等于acto S-1 ATP酶的周转速率。对于慢肌，ADP从acto S-1-ADP复合物中解离的速率也慢得多。先前已经表明，肌动球蛋白ATP酶（VM）的最大周转率与肌肉的收缩速度成正比。与VM相关的机制中的唯一步骤是S-1-产物状态与肌动蛋白形成复合物的表观二级速率常数。的证据进行了讨论的机制，其中释放的反应产物从肌动球蛋白的步骤是最重要的，在确定VM的值和收缩的速度。
The mechanism of ATP hydrolysis by myosin and actomyosin was investigated for the 4 major classes of vertebrate muscles: fast white (posterior latissimus dorsi), slow red (anterior latissimus dorsi), cardiac and smooth (gizzard). The kinetic behavior of all classes of muscle was consistent with the scheme developed previously for rabbit fast white muscle, but quantitative differences were observed for the rate constants of some of the steps in the hydrolysis cycle. The rate of the hydrolysis step of myosin subfragment-1 was similar for the striated muscles and 2 to 3 times smaller for smooth muscle. Two isomerizations of the enzyme occurred in the pathway leading to the formation of the myosin-products intermediate. The rate of dissociation of acto S-1 [myocin subfragment 1] by ATP was slower for slow muscles and a maximum rate was observed at low temperature. The rate of association of the S-1-products intermediate with actin was equal to the turnover rate of acto S-1 ATPase at low concentrations of actin. The rate of dissociation of ADP from an acto S-1-ADP complex was also much slower for slow muscle. It was shown previously that the maximum turnover rate of actomyosin ATPase (VM) is proportional to the velocity of contraction of the muscle. The only step in the mechanism that is correlated with VM is the apparent second-order rate constant for the formation of a complex of the S-1-product state with actin. The evidence is discussed in terms of a mechanism in which the release of reaction products from actomyosin is the step that is of primary importance in determining the value of VM and the velocity of contraction.