Crystallographic studies on the reaction of isopenicillin N synthase with an unsaturated substrate analogue
作者:Jonathan M. Elkins、Peter J. Rutledge、Nicolai I. Burzlaff、Ian J. Clifton、Robert M. Adlington、Peter L. Roach、Jack E. Baldwin
DOI:10.1039/b212270g
日期:2003.4.23
Isopenicillin N synthase (IPNS) catalyses conversion of the linear tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV) to isopenicillin N (IPN), the central step in biosynthesis of the beta-lactam antibiotics. The unsaturated substrate analogue delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-vinylglycine (ACvG) has previously been incubated with IPNS and single product was isolated, a 2-alpha-hydroxymethyl
异青霉素N合酶(IPNS)催化将线性三肽δ-(L-α-氨基己二酰基)-L-半胱氨酰-D-缬氨酸(ACV)转化为异青霉素N(IPN),这是生物合成β-内酰胺抗生素的关键步骤。先前已将不饱和底物类似物δ-(L-α-氨基己二酰基)-L-半胱氨酰-D-乙烯基甘氨酸(ACvG)与IPNS一起温育,并分离出单一产物,形成了2-α-羟甲基异青霉素N(HMPen),通过单加氧酶反应模式。ACvG现在已经用IPNS结晶,厌氧IPNS:Fe(II):ACvG络合物的结构确定为1.15 A分辨率。此外,通过将厌氧生长的晶体暴露于高压氧气中,以1.60A的分辨率获得了对应于双环产物HMPen的结构。根据这些以及其他IPNS结构,以及相关双加氧酶的最新发展,对由ACvG形成HMPen的[2 + 2]环加成机理进行了修订,并提出了逐步的自由基机理。修订后的机制与观察到的转化立体定向保持一致,但更适合于活性位铁原子周围配位几何的明显约束。