title: Catalytic mechanism of limonene epoxide hydrolase, a theoretical study.
abstract: The catalytic mechanism of limonene epoxide hydrolase (LEH) was investigated theoretically using the density functional theory method B3LYP. LEH is part of a novel limonene degradation pathway found in Rhodococcus erythropolis DCL14, where it catalyzes the hydrolysis of limonene-1,2-epoxide to give limonene-1,2-diol. The recent crystal structure of LEH was used to build a model of the LEH active site composed of five amino acids and a crystallographically observed water molecule. With this model, hydrolysis of different substrates was investigated. It is concluded that LEH employs a concerted general acid/general base-catalyzed reaction mechanism involving protonation of the substrate by Asp101, nucleophilic attack by water on the epoxide, and abstraction of a proton from water by Asp132. Furthermore, we provide an explanation for the experimentally observed regioselective hydrolysis of the four stereoisomers of limonene-1,2-epoxide.
authors.affiliation: Theoretical Chemistry, Department of Biotechnology, Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm, Sweden.
authors.forename: Kathrin H
authors.initials: KH
authors.lastname: Hopmann
authors.forename: B Martin
authors.initials: BM
authors.lastname: Hallberg
authors.forename: Fahmi
authors.initials: F
authors.lastname: Himo
mesh_terms: D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D000081005:Cyclohexane Monoterpenes; D004851:Epoxide Hydrolases / Q000037:antagonists & inhibitors / Q000737:chemistry*; D006860:Hydrogen Bonding; D006868:Hydrolysis; D008962:Models, Theoretical; D015394:Molecular Structure; D039821:Monoterpenes / Q000138:chemical synthesis / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014635:Valproic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D000081005:Cyclohexane Monoterpenes; D039821:Monoterpenes; C028940:limonene-1,2-epoxide; D014635:Valproic Acid; D004851:Epoxide Hydrolases; C115926:limonene-1,2-epoxide hydrolase; C004651:dipropylacetamide