Dash P K, Hackney D D
Department of Biological Sciences, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213.
Biochem Int. 1991 Dec;25(6):1013-22.
The mechanisms of increases in the ATPase rates of smooth muscle acto-myosin, acto-heavy meromyosin (HMM) and acto-subfragment 1 (S1) were investigated using steady state titration and 18O exchange. Phosphorylation increased the phosphate release rates both from acto-myosin and acto-HMM. Steady state titration at high enzyme concentrations and 18O exchange at substoichiometric ATP concentrations showed that gizzard myosin was kinetically homogeneous, whereas HMM and S1 prepared by various published methods were heterogeneous. At high ATP concentrations, a small population of HMM and S1 hydrolyzed ATP with a low amount of oxygen exchange.
利用稳态滴定法和18O交换法研究了平滑肌肌动球蛋白、肌动-重酶解肌球蛋白（HMM）和肌动-亚片段1（S1）的ATP酶活性增加的机制。磷酸化作用提高了肌动球蛋白和肌动-HMM的磷酸释放速率。在高酶浓度下的稳态滴定以及在亚化学计量ATP浓度下的18O交换表明，砂囊肌球蛋白在动力学上是均一的，而通过各种已发表方法制备的HMM和S1是不均一的。在高ATP浓度下，一小部分HMM和S1以低氧交换量水解ATP。
