McGuire J J, Rabinowitz J C
J Biol Chem. 1978 Feb 25;253(4):1079-85.
Two conflicting mechanisms have been proposed for formyltetrahydrofolate synthetase (EC 6.3.4.3). Detailed studies with a clostridial enzyme support a sequential mechanism, while a stepwise mechanism with formation of a dissociable intermediate has been proposed for the Peptococcus aerogenes synthetase. However, the data supporting the P. aerogenes mechanism were obtained using synthetase of questionable purity and the results supporting the mechanism could be attributed to contaminating activities. Consequently, uncertainty still exists with regard to the enzyme mechanism. To resolve this uncertainty, the P. aerogenes formyltetrahydrofolate synthetase has been purified to homogeneity and used in experiments to reinvestigate the reaction mechanism. The results of P1:ATP, ADP:ATP, and formate:10-formyltetrahydrofolate exchange experiments as well as a steady state kinetic analysis revealed no difference in the mechanisms of the P. aerogenes or clostridial synthetases. The results are inconsistent with a stepwise mechanism involving a dissociable intermediate and consistent only with a sequential mechanism.
关于甲酰四氢叶酸合成酶（EC 6.3.4.3），已经提出了两种相互矛盾的机制。对一种梭菌酶的详细研究支持一种顺序机制，而对于产气消化球菌合成酶，有人提出了一种形成可解离中间体的逐步机制。然而，支持产气消化球菌机制的数据是使用纯度存疑的合成酶获得的，支持该机制的结果可能归因于污染活性。因此，关于该酶的机制仍然存在不确定性。为了解决这种不确定性，产气消化球菌甲酰四氢叶酸合成酶已被纯化至同质，并用于实验以重新研究反应机制。P1：ATP、ADP：ATP和甲酸：10-甲酰四氢叶酸交换实验的结果以及稳态动力学分析表明，产气消化球菌或梭菌合成酶的机制没有差异。结果与涉及可解离中间体的逐步机制不一致，仅与顺序机制一致。
