Liu Meixia, Chen Chun-Chi, Chen Lu, Xiao Xiansha, Zheng Yingying, Huang Jian-Wen, Liu Weidong, Ko Tzu-Ping, Cheng Ya-Shan, Feng Xinxin, Oldfield Eric, Guo Rey-Ting, Ma Yanhe
College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, China.
Industrial Enzymes National Engineering Laboratory, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China.
Angew Chem Int Ed Engl. 2016 Apr 4;55(15):4721-4. doi: 10.1002/anie.201600656. Epub 2016 Feb 29.
We report the first X-ray structure of the unique "head-to-middle" monoterpene synthase, lavandulyl diphosphate synthase (LPPS). LPPS catalyzes the condensation of two molecules of dimethylallyl diphosphate (DMAPP) to form lavandulyl diphosphate, a precursor to the fragrance lavandulol. The structure is similar to that of the bacterial cis-prenyl synthase, undecaprenyl diphosphate synthase (UPPS), and contains an allylic site (S1) in which DMAPP ionizes and a second site (S2) which houses the DMAPP nucleophile. Both S-thiolo-dimethylallyl diphosphate and S-thiolo-isopentenyl diphosphate bind intact to S2, but are cleaved to (thio)diphosphate, in S1. His78 (Asn in UPPS) is essential for catalysis and is proposed to facilitate diphosphate release in S1, while the P1 phosphate in S2 abstracts a proton from the lavandulyl carbocation to form the LPP product. The results are of interest since they provide the first structure and structure-based mechanism of this unusual prenyl synthase.
我们报道了独特的“头对中”单萜合酶——薰衣草基二磷酸合酶（LPPS）的首个X射线结构。LPPS催化两分子二甲基烯丙基二磷酸（DMAPP）缩合形成薰衣草基二磷酸，薰衣草醇香料的前体。该结构与细菌顺式异戊二烯基合酶——十一异戊烯基二磷酸合酶（UPPS）的结构相似，包含一个烯丙基位点（S1），DMAPP在其中发生离子化，以及第二个位点（S2），用于容纳DMAPP亲核试剂。S-硫醇基二甲基烯丙基二磷酸和S-硫醇基异戊烯基二磷酸均完整地结合到S2，但在S1中被裂解为（硫代）二磷酸。His78（在UPPS中为Asn）对催化至关重要，推测其有助于在S1中释放二磷酸，而S2中的P1磷酸从薰衣草基碳正离子夺取一个质子以形成LPP产物。这些结果很有意义，因为它们提供了这种不寻常的异戊二烯基合酶的首个结构和基于结构的作用机制。
