Bagshaw C R, Trentham D R
J Supramol Struct. 1975;3(4):315-22. doi: 10.1002/jss.400030402.
From transient kinetic studies of the Mg2+-dependent adenosine triphosphatase of myosin subfragment 1, prepared from rabbit skeletal muscle, a seven-step mechanism has been proposed. Features of this mechanism include two-step processes for ATP and ADP binding in which the binary complex isomerizes in addition to a rapid nucleotide association step. In the case of ATP a large negative standard free energy change is associated with the isomerization. An overall rate-limiting isomerization of the myosin-product complex prior to product release has been identified. Studies on the mechanism of cleavage of ATP bound to the active site indicate the process is readily reversible and can account for the observation that more than one oxygen of the product phosphate arises from water. This proposal has been substantiated by the finding that the oxygen atoms of the gamma-phosphoryl group of bound ATP also undergo extensive exchange with water.
通过对从兔骨骼肌制备的肌球蛋白亚片段1的Mg2+依赖性三磷酸腺苷酶进行瞬态动力学研究，提出了一种七步机制。该机制的特点包括ATP和ADP结合的两步过程，其中二元复合物除了快速的核苷酸缔合步骤外还会异构化。就ATP而言，异构化伴随着很大的负标准自由能变化。已确定在产物释放之前肌球蛋白-产物复合物存在整体限速异构化。对结合在活性位点的ATP的裂解机制的研究表明该过程很容易逆转，并且可以解释产物磷酸中不止一个氧原子来自水的观察结果。结合的ATP的γ-磷酰基的氧原子也与水进行广泛交换这一发现证实了该提议。
