title: Dual catalytic role of the metal ion in nickel-assisted peptide bond hydrolysis.
abstract: In our previous research we demonstrated the sequence specific peptide bond hydrolysis of the R1-(Ser/Thr)-Xaa-His-Zaa-R2 in the presence of Ni(II) ions. The molecular mechanism of this reaction includes an N-O acyl shift of the R1 group from the Ser/Thr amine to the side chain hydroxyl group of this amino acid. The proposed role of the Ni(II) ion is to establish favorable geometry of the reacting groups. In this work we aimed to find out whether the crucial step of this reaction--the formation of the intermediate ester--is reversible. For this purpose we synthesized the test peptide Ac-QAASSHEQA-am, isolated and purified its intermediate ester under acidic conditions, and reacted it, alone, or in the presence of Ni(II) or Cu(II) ions at pH 8.2. We found that in the absence of either metal ion the ester was quickly and quantitatively (irreversibly) rearranged to the original peptide. Such reaction was prevented by either metal ion. Using Cu(II) ions as CD spectroscopic probe we showed that the metal binding structures of the ester and the final amine are practically identical. Molecular calculations of Ni(II) complexes indicated the presence of steric strain in the substrate, distorting the complex structure from planarity, and the absence of steric strain in the reaction products. These results demonstrated the dual catalytic role of the Ni(II) ion in this mechanism. Ni(II) facilitates the acyl shift by setting the peptide geometry, and prevents the reversal of the acyl shift, by stabilizing subsequent reaction products.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland.
authors.forename: Ewa Izabela
authors.initials: EI
authors.lastname: Podobas
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland.. Electronic address: abonna@ibb.waw.pl.
authors.forename: Arkadiusz
authors.initials: A
authors.lastname: Bonna
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Polkowska-Nowakowska
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland.. Electronic address: wbal@ibb.waw.pl.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Bal
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D003300:Copper / Q000737:chemistry; D004952:Esters; D006868:Hydrolysis; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D004952:Esters; D009842:Oligopeptides; D003300:Copper; D009532:Nickel
keywords: Acyl shift; Ni(II) complexes; Ni(II) molecular catalysis; Peptide bond hydrolysis