title: Modeling the Complete Catalytic Cycle of Aspartoacylase.
abstract: The complete catalytic cycle of aspartoacylase (ASPA), a zinc-dependent enzyme responsible for cleavage of N-acetyl-l-aspartate, is characterized by the methods of molecular modeling. The reaction energy profile connecting the enzyme-substrate (ES) and the enzyme-product (EP) complexes is constructed by the quantum mechanics/molecular mechanics (QM/MM) method assisted by the molecular dynamics (MD) simulations with the QM/MM potentials. Starting from the crystal structure of ASPA complexed with the intermediate analogue, the minimum-energy geometry configurations and the corresponding transition states are located. The stages of substrate binding to the enzyme active site and release of the products are modeled by MD calculations with the replica-exchange umbrella sampling technique. It is shown that the first reaction steps, nucleophilic attack of a zinc-bound nucleophilic water molecule at the carbonyl carbon and the amide bond cleavage, are consistent with the glutamate-assisted mechanism hypothesized for the zinc-dependent hydrolases. The stages of formation of the products, acetate and l-aspartate, and regeneration of the enzyme are characterized for the first time. The constructed free energy diagram from the reactants to the products suggests that the enzyme regeneration, but not the nucleophilic attack of the catalytic water molecule, corresponds to the rate-determining stage of the full catalytic cycle of ASPA.
authors.affiliation: Chemistry Department, M.V. Lomonosov Moscow State University , Leninskie Gory 1/3, Moscow 119991, Russian Federation.|N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences , Kosygina 4, Moscow 119334, Russian Federation.
authors.forename: Ekaterina D
authors.initials: ED
authors.lastname: Kots
authors.affiliation: Chemistry Department, M.V. Lomonosov Moscow State University , Leninskie Gory 1/3, Moscow 119991, Russian Federation.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Khrenova
authors.affiliation: N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences , Kosygina 4, Moscow 119334, Russian Federation.
authors.forename: Sofya V
authors.initials: SV
authors.lastname: Lushchekina
authors.affiliation: Chemistry Department, M.V. Lomonosov Moscow State University , Leninskie Gory 1/3, Moscow 119991, Russian Federation.|N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences , Kosygina 4, Moscow 119334, Russian Federation.
authors.forename: Sergei D
authors.initials: SD
authors.lastname: Varfolomeev
authors.affiliation: Chemistry Department, M.V. Lomonosov Moscow State University , Leninskie Gory 1/3, Moscow 119991, Russian Federation.|N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences , Kosygina 4, Moscow 119334, Russian Federation.
authors.forename: Bella L
authors.initials: BL
authors.lastname: Grigorenko
authors.affiliation: Chemistry Department, M.V. Lomonosov Moscow State University , Leninskie Gory 1/3, Moscow 119991, Russian Federation.|N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences , Kosygina 4, Moscow 119334, Russian Federation.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Nemukhin
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism*; D001224:Aspartic Acid / Q000737:chemistry / Q000378:metabolism; D055162:Biocatalysis; D020134:Catalytic Domain; D008958:Models, Molecular; D011789:Quantum Theory; D013816:Thermodynamics; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000737:chemistry / Q000378:metabolism
chemical_list: D014867:Water; D001224:Aspartic Acid; D000581:Amidohydrolases; C019751:aspartoacylase; D015032:Zinc