Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan.
Org Biomol Chem. 2010 Mar 7;8(5):1106-10. doi: 10.1039/b918656e. Epub 2010 Jan 6.
Asparagus officinalis hinokiresinol synthase (HRS) is composed of two subunits, HRSalpha and HRSbeta. Individually, each subunit forms (E)-hinokiresinol (EHR) from 4-coumaryl 4-coumarate, whereas a mixture of both subunits forms (Z)-hinokiresinol (ZHR) from the same substrate. In this study, we analyzed the enantiomeric compositions of ZHR and EHR formed after incubation of 4-coumaryl 4-coumarate with recombinant subunit proteins, recHRSalpha and/or recHRSbeta, and with naturally occurring A. officinalis ZHR. The enantiomeric composition of ZHR formed by the mixture of recHRSalpha and recHRSbeta was (+)-100% enantiomer excess (e.e.), identical to that of A. officinalis ZHR. In contrast, the enantiomeric compositions of EHR formed by recHRSalpha and recHRSbeta, individually, were (-)-20.6 and (-)-9.0% e.e., respectively. These results clearly demonstrate that the subunit composition of A. officinalis HRS controls not only cis/trans isomerism but also enantioselectivity in hinokiresinol formation.
天门冬酰苯丙氨酸甲酯合成酶（HRS）由两个亚基，HRSalpha 和 HRSbeta 组成。每个亚基都能将 4-香豆酰 4-香豆酸转化为（E）-松脂醇（EHR），而两个亚基的混合物则能将同一底物转化为（Z）-松脂醇（ZHR）。在这项研究中，我们分析了用重组亚基蛋白 recHRSalpha 和/或 recHRSbeta 以及天然天门冬酰苯丙氨酸甲酯合成酶（ZHR）孵育 4-香豆酰 4-香豆酸后形成的 ZHR 和 EHR 的对映体组成。recHRSalpha 和 recHRSbeta 混合物形成的 ZHR 的对映体组成是（+）-100%对映体过量（ee），与天门冬酰苯丙氨酸甲酯合成酶（ZHR）相同。相比之下，recHRSalpha 和 recHRSbeta 分别单独形成的 EHR 的对映体组成分别为（-）-20.6%和（-）-9.0%ee。这些结果清楚地表明，天门冬酰苯丙氨酸甲酯合成酶的亚基组成不仅控制了顺/反异构，还控制了松脂醇形成的对映选择性。
