Hageman R V, Burris R H
J Biol Chem. 1979 Nov 25;254(22):11189-92.
During the lag period before H2 is evolved by the nitrogenase system, the EPR signal of dinitrogenase decreases steadily, indicating transfer of electrons into dinitrogenase. The rate constant for the decrease in amplitude of the EPR signal, the steady state rate of H2 evolution from nitrogenase, and the length of the lag period have been measured. The data suggest that H2 is evolved only after dinitrogenase has been reduced by 2 electrons/molybdenum. The electrons that have been transfered into dinitrogenase during the lag period are not evolved as H2 upon denaturation of dinitrogenase. The existence of a lag indicates that the two nitrogenase proteins dissociate after every electron transfer. The lag occurs and the nitrogenase proteins dissociate under a variety of conditions of pH and temperature.
在固氮酶系统释放H2之前的延迟期内，固氮酶的电子顺磁共振（EPR）信号稳步下降，表明电子转移到了固氮酶中。已经测量了EPR信号幅度降低的速率常数、固氮酶释放H2的稳态速率以及延迟期的长度。数据表明，只有在每个钼原子结合2个电子的情况下，固氮酶 将H2释放出来。在延迟期内转移到固氮酶中的电子，在固氮酶变性后不会以H2的形式释放出来。延迟期的存在表明，每进行一次电子转移后，两种固氮酶蛋白就会解离。在各种pH值和温度条件下都会出现延迟期，固氮酶蛋白也会发生解离。
