title: Combined X-ray diffraction and QM/MM study of the Burkholderia cepacia lipase-catalyzed secondary alcohol esterification.
abstract: To understand the origin of high enantioselectivity of Burkholderia cepacia lipase (BCL) toward secondary alcohol, (R,S)-1-phenoxy-2-hydroxybutane (1), and its ester (E1), we determined the crystal structure of BCL complexed with phosphonate analogue of S-E1 and accomplished a series of MM, MC, and QM/MM studies. We have found that the inhibitor in the S configuration binds into the BCL active site in the same manner as the R isomer, with an important difference: while in case of the R-inhibitor the H-bond between its alcohol oxygen and catalytic His286 can be formed, in the case of the S-inhibitor this is not possible. Molecular modeling for both E1 enantiomers revealed orientations in which all hydrogen bonds characteristic of productive binding are formed. To check the possibility of chemical transformation, four different orientations of the substrate (two for each enantiomer) were chosen, and a series of ab initio QM/MM calculations were accomplished. Starting from the covalent complex, we modeled the ester (E1) hydrolysis and the alcohol (1) esterification. The calculations revealed that ester release is possible starting with all four covalent complexes. Alcohol release from the BCL-E1 complex in which the S-substrate is bound in the same manner as the S-inhibitor in the crystal structure however is not possible. These results show that the crystallographically determined binding modes should be taken with caution when modeling chemical reactions.
authors.affiliation: Rudjer Bosković Institute, Bijenicka 54, HR-10000 Zagreb, Croatia, Belupo dd, Danica 5, HR-48000 Koprivnica, Croatia. marija.luic@irb.hr
authors.forename: Marija
authors.initials: M
authors.lastname: Luić
authors.forename: Zoran
authors.initials: Z
authors.lastname: Stefanić
authors.forename: Igor
authors.initials: I
authors.lastname: Ceilinger
authors.forename: Milan
authors.initials: M
authors.lastname: Hodoscek
authors.forename: Dusanka
authors.initials: D
authors.lastname: Janezic
authors.forename: Tihana
authors.initials: T
authors.lastname: Lenac
authors.forename: Ivana Lescić
authors.initials: IL
authors.lastname: Asler
authors.forename: Dragan
authors.initials: D
authors.lastname: Sepac
authors.forename: Sanja
authors.initials: S
authors.lastname: Tomić
mesh_terms: D000438:Alcohols / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D040761:Biomimetic Materials / Q000737:chemistry / Q000378:metabolism; D016956:Burkholderia cepacia / Q000201:enzymology*; D002384:Catalysis; D018360:Crystallography, X-Ray; D004951:Esterification; D006860:Hydrogen Bonding; D008049:Lipase / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D014961:X-Ray Diffraction
chemical_list: D000438:Alcohols; D010710:Phosphates; D008049:Lipase