Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
FEBS Lett. 2013 Aug 19;587(16):2705-9. doi: 10.1016/j.febslet.2013.07.016. Epub 2013 Jul 13.
Isopenicillin N synthase (IPNS) is a non-heme iron oxidase central to the biosynthesis of β-lactam antibiotics. IPNS converts the tripeptide δ-(L-α-aminoadipoyl)-L-cysteinyl-D-valine (ACV) to isopenicillin N while reducing molecular oxygen to water. The substrate analogue δ-(L-α-aminoadipoyl)-L-cysteinyl-O-methyl-D-threonine (ACmT) is not turned over by IPNS. Epimeric δ-(L-α-aminoadipoyl)-L-cysteinyl-O-methyl-D-allo-threonine (ACmaT) is converted to a bioactive penam product. ACmT and ACmaT differ from each other only in the stereochemistry at the β-carbon atom of their third residue. These substrates both contain a methyl ether in place of the isopropyl group of ACV. We report an X-ray crystal structure for the anaerobic IPNS:Fe(II):ACmT complex. This structure reveals an additional water molecule bound to the active site metal, held by hydrogen-bonding to the ether oxygen atom of the substrate analogue.
异青霉素 N 合酶（IPNS）是一种非血红素铁氧化酶，是β-内酰胺类抗生素生物合成的核心。IPNS 将三肽 δ-（L-α-氨基己二酰基）-L-半胱氨酸-D-缬氨酸（ACV）转化为异青霉素 N，同时将分子氧还原为水。底物类似物 δ-（L-α-氨基己二酰基）-L-半胱氨酸-O-甲基-D-苏氨酸（ACmT）不能被 IPNS 转化。差向异构体 δ-（L-α-氨基己二酰基）-L-半胱氨酸-O-甲基-D-allo-苏氨酸（ACmaT）被转化为生物活性 penam 产物。ACmT 和 ACmaT 仅在第三个残基的β-碳原子的立体化学上有所不同。这些底物都在 ACV 的异丙基位置上含有一个甲基醚。我们报告了厌氧 IPNS：Fe（II）：ACmT 复合物的 X 射线晶体结构。该结构揭示了一个额外的水分子与活性位点金属结合，通过氢键与底物类似物的醚氧原子结合。
