Howard-Jones Annaleise R, Elkins Jonathan M, Clifton Ian J, Roach Peter L, Adlington Robert M, Baldwin Jack E, Rutledge Peter J
Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
Biochemistry. 2007 Apr 24;46(16):4755-62. doi: 10.1021/bi062314q. Epub 2007 Mar 31.
Isopenicillin N synthase (IPNS), a non-heme iron oxidase central to penicillin and cephalosporin biosynthesis, catalyzes an energetically demanding chemical transformation to produce isopenicillin N from the tripeptide delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-valine (ACV). We describe the synthesis of two cyclopropyl-containing tripeptide analogues, delta-(l-alpha-aminoadipoyl)-l-cysteinyl-beta-methyl-d-cyclopropylglycine and delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-cyclopropylglycine, designed as probes for the mechanism of IPNS. We have solved the X-ray crystal structures of these substrates in complex with IPNS and propose a revised mechanism for the IPNS-mediated turnover of these compounds. Relative to the previously determined IPNS-Fe(II)-ACV structure, key differences exist in substrate orientation and water occupancy, which allow for an explanation of the differences in reactivity of these substrates.
异青霉素N合酶（IPNS）是青霉素和头孢菌素生物合成过程中的一种非血红素铁氧化酶，它催化一种能量需求较高的化学转化反应，从三肽δ-（L-α-氨基己二酰基）-L-半胱氨酰-D-缬氨酸（ACV）生成异青霉素N。我们描述了两种含环丙基的三肽类似物δ-（L-α-氨基己二酰基）-L-半胱氨酰-β-甲基-D-环丙基甘氨酸和δ-（L-α-氨基己二酰基）-L-半胱氨酰-D-环丙基甘氨酸的合成，它们被设计用作研究IPNS作用机制的探针。我们解析了这些底物与IPNS复合物的X射线晶体结构，并提出了IPNS介导这些化合物周转的修正机制。相对于先前确定的IPNS-Fe（II）-ACV结构，底物取向和水占有率存在关键差异，这可以解释这些底物反应性的差异。
