Janson C A, Degani C, Boyer P D
J Biol Chem. 1979 May 25;254(10):3743-9.
Yeast inorganic pyrophosphatase, with 10 mM 32Pi and 10 mM Mg2+ present at pH 7.3 TO 7.6, rapidly forms enzyme-bound pyrophosphate equivalent to about 5% of the total catalytic sties on the two enzyme subunits. The enzyme thus appears to bind PPi so as to favor thermodynamically its formation from Pi. The enzyme catalyzes a measurable equilibrium formation of free PPi at a much slower rate. Under similar conditions, the enzyme catalyzes a rapid exchange of oxygen atoms between Pi and water with the relative activation by metals being Mg2+ greater than Zn2+ greater than Co2+ greater than Mn2+. Millisecond mixing and quenching experiments demonstrate that the rate of formation and cleavage of the enzyme-bound PPi is rapid enough to explain most or all of the oxygen exchange reaction.
在pH 7.3至7.6、存在10 mM 32Pi和10 mM Mg2+的条件下，酵母无机焦磷酸酶能迅速形成与两个酶亚基上约5%的总催化位点相当的酶结合焦磷酸。因此，该酶似乎结合PPi，从而在热力学上有利于其由Pi形成。该酶以慢得多的速率催化游离PPi的可测量平衡形成。在类似条件下，该酶催化Pi和水之间氧原子的快速交换，金属的相对活化作用为Mg2+大于Zn2+大于Co2+大于Mn2+。毫秒级混合和淬灭实验表明，酶结合PPi的形成和裂解速率足够快，足以解释大部分或全部氧交换反应。
