Modulating pyridoxamine-mediated transamination through a beta beta alpha motif peptide scaffold

A pyridoxamine coenzyme amino acid chimera (Pam) was incorporated into a de signed beta beta alpha motif peptide to explore the ability of a small synt hetic peptide scaffold to influence coenzyme mediated transamination. Struc tural characterization of this peptide by CD and NMR spectroscopy suggested that the pyridoxamine containing residue was accommodated into the sheet r egion of the motif without gross structural perturbations. To investigate t he ability of the peptide architecture to influence the amount and distribu tion of transamination product in the conversion of pyruvic acid to alanine , a family of 18 related peptides, CBP01-CBP18, was rapidly synthesized and purified in parallel. These peptides were designed to generate different p eptide environments for the pyridoxamine functionality within the context o f the structured beta beta alpha peptide motif. Studies of peptide-mediated transamination revealed clear trends in stereospecific production of L-ala nine as a function of substitutions at positions five and seven of the moti f. Furthermore, new trends favoring the other enantiomeric product resulted from the addition of copper(II) ion, a known chelator of the transaminatio n reaction intermediates. In the presence of copper(II) ion the amount of a lanine product generated was increased by up to 32-fold relative to a pyrid oxamine model compound in the presence of copper(II) ion. These functional results, accompanied by further CD and NMR spectroscopic analysis of CBP14, one of the CBP family of peptides, suggest that small synthetic beta beta alpha motif peptides can be used to influence the functional properties of coenzymes. (C) 1999 Elsevier Science Ltd. All rights reserved.