TAILIEUCHUNG - Báo cáo khoa học: Do N-terminal nucleophile hydrolases indeed have a single amino acid catalytic center? Supporting amino acid residues at the active site of penicillin G acylase

A new set of experimental kinetic data on the hydrolysis of a series of phenylacetylp-substituted anilides catalyzed by penicillin G acylase from Escherichia coli(PGA) is presented in this article. The Hammett plot of log(kcat,R ⁄kcat,H) versus rp ) has three linear segments, which distinguishes the enzyme from the other N-terminal nucleophile hydrolases for which data are available. | ỊFEBS Journal Do N-terminal nucleophile hydrolases indeed have a single amino acid catalytic center Supporting amino acid residues at the active site of penicillin G acylase Diana Zhiryakova1 Ivaylo Ivanov2 Sonya Ilieva3 Maya Guncheva1 Boris Galunsky4 and Nicolina Stambolieva1 1 Institute of Organic Chemistry with Center of Phytochemistry Bulgarian Academy of Sciences Sofia Bulgaria 2 Faculty of Biology University of Sofia Sv. Kl. Ohridski Bulgaria 3 Faculty of Chemistry University of Sofia Sv. Kl. Ohridski Bulgaria 4 Institute of TechnicalBiocatalysis Hamburg University of Technology Germany Keywords catalytic mechanism Hammett plot N-terminalnucleophile Ntn hydrolase penicillin G acylase quantum mechanical QM and molecular mechanical MM modeling Correspondence D. Zhiryakova Institute of Organic Chemistry with Center of Phytochemistry Bulgarian Academy of Sciences 9 Acad. G. Bonchev str. 1113 Sofia Bulgaria Fax 359 2 870 0225 Tel 359 2 9606 160 E-mail diana_zh@ Received 25 September 2008 revised 28 January 2009 accepted 27 February 2009 doi A new set of experimental kinetic data on the hydrolysis of a series of phenylacetyl p-substituted anilides catalyzed by penicillin G acylase from Escherichia coli PGA is presented in this article. The Hammett plot of log kcat R kcat H versus rp has three linear segments which distinguishes the enzyme from the other N-terminal nucleophile hydrolases for which data are available. Three amino acids in the vicinity of the catalytic SerB1 AsnB241 AlaB69 and GlnB23 were included in the quantum mechanical model. The stable structures and the transition states for acylation were optimized by molecular mechanical modeling and at the AM1 level of theory for three model substrates with H a methoxy group or a nitro group in the para position in the leaving group . Intrinsic interactions of several functional groups at the active site of PGA are discussed in relation to the catalytic efficiency of

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