title: QM/MM study of the mechanism of enzymatic limonene 1,2-epoxide hydrolysis.
abstract: Limonene 1,2-epoxide hydrolase (LEH) is completely different from those of classic epoxide hydrolases (EHs) which catalyze the hydrolysis of epoxides to vicinal diols. A novel concerted general acid catalysis step involving the Asp101-Arg99-Asp132 triad is proposed to play an important role in the mechanism. Combined quantum-mechanical/molecular-mechanical (QM/MM) calculations gave activation barriers of 16.9 and 25.1kcal/mol at the B3LYP/6-31G(d,p)//CHARMM level for nucleophilic attack on the more and less substituted epoxide carbons, respectively. Furthermore, the important roles of residues Arg99, Tyr53 and Asn55 on mutated LEH were evaluated by QM/MM-scanned energy mapping. These results may provide an explanation for site-directed mutagenesis.
authors.affiliation: Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong, China.
authors.forename: Q Q
authors.initials: QQ
authors.lastname: Hou
authors.forename: X
authors.initials: X
authors.lastname: Sheng
authors.forename: J H
authors.initials: JH
authors.lastname: Wang
authors.forename: Y J
authors.initials: YJ
authors.lastname: Liu
authors.forename: C B
authors.initials: CB
authors.lastname: Liu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055162:Biocatalysis; D020134:Catalytic Domain; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D000081005:Cyclohexane Monoterpenes; D004851:Epoxide Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D008958:Models, Molecular; D039821:Monoterpenes / Q000737:chemistry / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011789:Quantum Theory; D012240:Rhodococcus / Q000201:enzymology*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D000081005:Cyclohexane Monoterpenes; D039821:Monoterpenes; C028940:limonene-1,2-epoxide; D004851:Epoxide Hydrolases; C115926:limonene-1,2-epoxide hydrolase