Pferrer S, Kulik R, Hiller T, Kuhn H J
Abteilung für Allgemeine Physiologie, Universität Ulm, Federal Republic of Germany.
Biophys J. 1988 Feb;53(2):127-35. doi: 10.1016/S0006-3495(88)83074-1.
The dependence of the isometric tension, the velocity of unloaded shortening, and the steady-state rate of MgATP hydrolysis on the MgATP concentration (range 0.01-5 mM MgATP) was studied in Ca-activated skinned Limulus muscle fibers. With increasing MgATP concentration the isometric tension increased to a peak at approximately 0.1 mM, and slightly decreased in the range up to 5 mM MgATP. The velocity of unloaded shortening depended on the MgATP concentration roughly according to the Michaelis-Menten law of saturation kinetics with a Michaelis-Menten constant Kv = 95 microM and a maximum shortening velocity of 0.07 muscle lengths s-1; the detachment rate of the cross-bridges during unloaded shortening was 24 s-1. The rate of MgATP splitting also depended hyperbolically on the MgATP concentration with a Michaelis-Menten constant Ka = 129 microM and a maximum turnover frequency of 0.5-1 s-1. The results are discussed in terms of a cross-bridge model based on a biochemical scheme of ATP hydrolysis by actin and myosin in solution.
在经钙激活的去皮鲎肌纤维中，研究了等长张力、无负荷缩短速度以及MgATP水解的稳态速率对MgATP浓度（范围为0.01 - 5 mM MgATP）的依赖性。随着MgATP浓度的增加，等长张力在约0.1 mM时增加至峰值，并在高达5 mM MgATP的范围内略有下降。无负荷缩短速度大致根据米氏饱和动力学定律依赖于MgATP浓度，米氏常数Kv = 95 microM，最大缩短速度为0.07肌肉长度/秒；无负荷缩短过程中横桥的解离速率为24秒^-1。MgATP水解速率也呈双曲线依赖于MgATP浓度，米氏常数Ka = 129 microM，最大周转频率为0.5 - 1秒^-1。根据基于肌动蛋白和肌球蛋白在溶液中ATP水解生化机制的横桥模型对结果进行了讨论。
