Abstract.
The hydrolysis of glycylglycine (GylGly), glycyl-L-leucine (GlyLeu), L-leucylglycine (LeuGly) and glycyl-DL-serine (GlySer) promoted by a copper(II)-cis,cis-1,3,5-triaminocyclohexane complex [Cu(II)TACH] was investigated at 70 °C and pH 7–10, using HPLC. The observed pseudo-first-order rate constants (k obs) and rate enhancing factors (REF) were as follows: 4.1×10–3 h–1 (REF=23) for GylGly, 1.6×10–3 h–1 (REF=21) for GlyLeu, 5.1×10–3 h–1 (REF=64) for LeuGly and 9.2×10–2 h–1 (REF=47) for GlySer [pH 8.1, dipeptide 2 mM, copper(II) 2 mM and TACH 2 mM]. Based on the pH dependence and dipeptide concentration dependence of the initial rates and speciation of the Cu(II)-TACH-dipeptide system at 25 °C and I=0.1, the reactions proceed via the formation of a ternary complex [Cu(TACH)(dipeptide)]+ as an intermediate followed by OH–-dependent and OH–-independent paths to give amino acid(s). GylGly, GlyLeu and LeuGly preferred the OH–-dependent path, while GlySer preferred the OH–-independent path. The latter can be explained by the intramolecular attack of the amide carbonyl group coordinated with its oxygen atom by the OH group in the serine residue. The X-ray crystal structure of [Cu(TACH)(GlyGly)]BPh4·MeOH confirmed that GlyGly coordinates to copper(II) ion with its terminal amino N and amide O atoms. The crystal structures of [Cu(TACH)(Gly)]BPh4 and [Cu2(TACH)2(OH)2](ClO4)2·NaClO4·H2O are also reported. Electronic supplementary material to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00775-002-0368-9.
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Fujii, Y., Kiss, T., Gajda, T. et al. Copper(II)-cis,cis-1,3,5-triaminocyclohexane complex-promoted hydrolysis of dipeptides: kinetic, speciation and structural studies. J Biol Inorg Chem 7, 843–851 (2002). https://doi.org/10.1007/s00775-002-0368-9
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DOI: https://doi.org/10.1007/s00775-002-0368-9