title: Insights into the Lactonase Mechanism of Serum Paraoxonase 1 (PON1): Experimental and Quantum Mechanics/Molecular Mechanics (QM/MM) Studies.
abstract: Serum paraoxonase 1 (PON1) is a versatile enzyme for the hydrolysis of various substrates (e.g., lactones, phosphotriesters) and for the formation of a promising chemical platform γ-valerolactone. Elucidation of the PON1-catalyzed lactonase reaction mechanism is very important for understanding the enzyme function and for engineering this enzyme for specific applications. Kinetic study and hybrid quantum mechanics/molecular mechanics (QM/MM) method were used to investigate the PON1-catalyzed lactonase reaction of γ-butyrolactone (GBL) and (R)-γ-valerolactone (GVL). The activation energies obtained from the QM/MM calculations were in good agreement with the experiments. Interestingly, the QM/MM energy barriers at MP2/3-21G(d,p) level for the lactonase of GVL and GBL were respectively 14.3-16.2 and 11.5-13.1 kcal/mol, consistent with the experimental values (15.57 and 14.73 kcal/mol derived from respective kcat values of 36.62 and 147.21 s(-1)). The QM/MM energy barriers at MP2/6-31G(d) and MP2/6-31G(d,p) levels were also in relatively good agreements with the experiments. Importantly, the difference in the QM/MM energy barriers at MP2 level with all investigated basis sets for the lactonase of GVL and GBL were in excellent agreement with the experiments (0.9-3.1 and 0.8 kcal/mol, respectively). A detailed mechanism for the PON1-catalyzed lactonase reaction was also proposed in this study.
authors.affiliation: †Department of Chemical Engineering and ‡Department of Chemistry, Kwangwoon University, Seoul 139-701, Republic of Korea.
authors.forename: Quang Anh Tuan
authors.initials: QA
authors.lastname: Le
authors.affiliation: †Department of Chemical Engineering and ‡Department of Chemistry, Kwangwoon University, Seoul 139-701, Republic of Korea.
authors.forename: Seonghoon
authors.initials: S
authors.lastname: Kim
authors.affiliation: †Department of Chemical Engineering and ‡Department of Chemistry, Kwangwoon University, Seoul 139-701, Republic of Korea.
authors.forename: Rakwoo
authors.initials: R
authors.lastname: Chang
authors.affiliation: †Department of Chemical Engineering and ‡Department of Chemistry, Kwangwoon University, Seoul 139-701, Republic of Korea.
authors.forename: Yong Hwan
authors.initials: YH
authors.lastname: Kim
mesh_terms: D015107:4-Butyrolactone / Q000378:metabolism; D043303:Aryldialkylphosphatase / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D055162:Biocatalysis; D007700:Kinetics; D007783:Lactones / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D007783:Lactones; D043303:Aryldialkylphosphatase; C037556:gamma-valerolactone; D015107:4-Butyrolactone