Scott R H, Sperl G T, DeMoss J A
J Bacteriol. 1979 Feb;137(2):719-26. doi: 10.1128/jb.137.2.719-726.1979.
When Escherichia coli was grown in the presence of tungstate, inactive forms of two molybdoenzymes, nitrate reductase and formate dehydrogenase, accumulated and were converted to their active forms upon incubation of cell suspensions with molybdate and chloramphenicol. The conversion to the active enzymes did not occur in cell extracts. When incubated with [(99)Mo]molybdate and chloramphenicol, the tungstate-grown cells incorporated (99)Mo into protein components which were released from membranes by procedures used to release nitrate reductase and formate dehydrogenase and which migrated with these activities on polyacrylamide gels. Although neither activity was formed during incubation of the crude extract with molybdate, (99)Mo was incorporated into protein components which were released from the membrane fraction under the same conditions and were similar to the active enzymes in their electrophoretic properties. The in vitro incorporation of (99)Mo occurred specifically into these components and was equal to or greater than the amount incorporated in vivo under the same conditions. Molybdenum in preformed, active nitrate reductase and formate dehydrogenase did not exchange with [(99)Mo]molybdate, demonstrating that the observed incorporation depended on the demolybdo forms of the enzymes. We conclude that molybdate may be incorporated into the demolybdo forms both in vivo and in vitro; some unknown additional factor or step, required for active enzyme formation, occurs in vivo but not in vitro under the conditions employed.
当大肠杆菌在钨酸盐存在的情况下生长时，两种钼酶（硝酸还原酶和甲酸脱氢酶）的无活性形式会积累，并且在细胞悬浮液与钼酸盐和氯霉素一起孵育后会转化为它们的活性形式。这种向活性酶的转化在细胞提取物中不会发生。当与[(99)Mo]钼酸盐和氯霉素一起孵育时，在钨酸盐存在下生长的细胞将(99)Mo掺入蛋白质组分中，这些蛋白质组分通过用于释放硝酸还原酶和甲酸脱氢酶的方法从膜中释放出来，并且在聚丙烯酰胺凝胶上与这些活性一起迁移。尽管在粗提取物与钼酸盐孵育期间没有形成任何一种活性，但(99)Mo被掺入在相同条件下从膜部分释放的蛋白质组分中，并且在电泳性质上与活性酶相似。(99)Mo的体外掺入特异性地发生在这些组分中，并且等于或大于在相同条件下体内掺入的量。预先形成的活性硝酸还原酶和甲酸脱氢酶中的钼不会与[(99)Mo]钼酸盐交换，这表明观察到的掺入取决于酶的脱钼形式。我们得出结论，钼酸盐在体内和体外都可能掺入到脱钼形式中；活性酶形成所需的一些未知的额外因素或步骤在体内发生，但在所采用的条件下在体外不发生。
