title: Reaction mechanism and free energy profile for acylation of Candida Antarctica lipase B with methylcaprylate and acetylcholine: density functional theory calculations.
abstract: Candida Antarctica lipase B (CALB), a specific enzyme to catalyze the hydrolysis of esters, can be a good candidate for acetylcholine (ACh) hydrolysis instead of acetylcholinesterase. The catalytic mechanism of the CALB acylation, as the first stage in the hydrolysis reaction, with ACh and methylcaprylate (MEC) has been examined by using density functional theory technique. The significant emphasis of this article is on the free energy barriers for the acylation step of hydrolysis reactions. Computed free energy barriers of the first step are 9.2 and 15.9 kcal mol(-1), but for the second step are 7.9 and 11.6 kcal mol(-1) for MEC and ACh respectively. Activation free energies are in the comparable and acceptable range and imply both of two reactions are theoretically possible. The stability role of the adjacent amino acids was examined by using two applied tools. It is exposed that the oxyanion hole residues decrease energy barriers by stabilizing the transition state structures.
authors.affiliation: Biophysical chemistry laboratory, Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran. Electronic address: sadeghi.mohammadsadegh@gmail.com.
authors.forename: Mohammad Sadegh Sadeghi
authors.initials: MS
authors.lastname: Googheri
authors.affiliation: Biophysical chemistry laboratory, Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran; Research and Technology Center of Biomolecules, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Housaindokht
authors.affiliation: Department of Chemistry, University of Isfahan, Isfahan, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Sabzyan
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000215:Acylation; D002210:Caprylates / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D008049:Lipase / Q000378:metabolism*
chemical_list: D002210:Caprylates; D005656:Fungal Proteins; D008049:Lipase; C431349:lipase B, Candida antarctica; D000109:Acetylcholine
keywords: Activation energy; Catalytic hydrolysis; Enzyme-substrate interaction; MD simulation; QM investigation