Marolewski A E, Mattia K M, Warren M S, Benkovic S J
Department of Chemistry, The Pennsylvania State University, University Park 16802, USA.
Biochemistry. 1997 Jun 3;36(22):6709-16. doi: 10.1021/bi962961p.
The Escherichia coli purT encoded glycinamide ribonucleotide transformylase (GAR transformylase) serves as an alternate enzyme in the production of formyl GAR for use in de novo purine biosynthesis. This enzyme differs from the previously known purN encoded enzyme in size, sequence, and substrates; ATP and formate are required as opposed to formyl tetrahydrofolate. Kinetic studies of the wild-type PurT enzyme described here demonstrate that formyl phosphate behaves as a chemically and kinetically competent intermediate. The requirement for ATP and GAR in these reactions is consistent with previous steady-state kinetic results, which demonstrated that all substrates must be bound before catalysis. Kinetic characterization of a mutant, which releases formyl phosphate into solution, and positional isotope exchange studies also support the assignment of formyl phosphate as a plausible intermediate.
大肠杆菌purT编码的甘氨酰胺核糖核苷酸转甲酰基酶（GAR转甲酰基酶）在从头嘌呤生物合成中用于生成甲酰基GAR的过程中作为一种替代酶发挥作用。该酶在大小、序列和底物方面与先前已知的purN编码酶不同；与甲酰四氢叶酸相反，需要ATP和甲酸。此处描述的野生型PurT酶的动力学研究表明，甲酰磷酸作为一种化学和动力学上合适的中间体发挥作用。这些反应中对ATP和GAR的需求与先前的稳态动力学结果一致，先前的结果表明所有底物必须在催化之前结合。对一种将甲酰磷酸释放到溶液中的突变体的动力学表征以及位置同位素交换研究也支持将甲酰磷酸指定为一种合理的中间体。
