title: Structures of Iridoid Synthase from Cantharanthus roseus with Bound NAD(+) , NADPH, or NAD(+) /10-Oxogeranial: Reaction Mechanisms.
abstract: Structures of the iridoid synthase nepetalactol synthase in the presence of NAD(+) , NADPH or NAD(+) /10-oxogeranial were solved. The 10-oxogeranial substrate binds in a transoid-O1-C3 conformation and can be reduced by hydride addition to form the byproduct S-10-oxo-citronellal. Tyr178 Oζ is positioned 2.5 Å from the substrate O1 and provides the second proton required for reaction. Nepetalactol product formation requires rotation about C1-C2 to form the cisoid isomer, leading to formation of the cis-enolate, together with rotation about C4-C5, which enables cyclization and lactol production. The structure is similar to that of progesterone-5β-reductase, with almost identical positioning of NADP, Lys146(147), Tyr178(179), and F342(343), but only Tyr178 and Phe342 appear to be essential for activity. The transoid 10-oxogeranial structure also serves as a model for β-face hydride attack in progesterone 5β-reductases and is of general interest in the context of asymmetric synthesis.
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Yumei
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Weidong
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Chemistry, University of Illinois, Urbana, IL 61801, USA.
authors.forename: Satish R
authors.initials: SR
authors.lastname: Malwal
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, University of Illinois, Urbana, IL 61801, USA.
authors.forename: Xinxin
authors.initials: X
authors.lastname: Feng
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Tzu-Ping
authors.initials: TP
authors.lastname: Ko
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Chun-Chi
authors.initials: CC
authors.lastname: Chen
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Zhongxia
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Meixia
authors.initials: M
authors.lastname: Liu
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Han
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Gao
authors.affiliation: Department of Chemistry, University of Illinois, Urbana, IL 61801, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Oldfield
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Rey-Ting
authors.initials: RT
authors.lastname: Guo
mesh_terms: D000080462:Acyclic Monoterpenes; D029062:Apocynaceae / Q000201:enzymology*; D039823:Iridoids / Q000737:chemistry*; D008025:Ligases / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D039821:Monoterpenes / Q000737:chemistry*; D009243:NAD / Q000737:chemistry*; D009249:NADP / Q000737:chemistry*
chemical_list: D000080462:Acyclic Monoterpenes; D039823:Iridoids; D039821:Monoterpenes; D009243:NAD; D009249:NADP; D008025:Ligases; C007076:citral
keywords: X-ray crystallography; biosynthesis; enzyme mechanisms; monoterpenes; natural products