Functionalised bilayer vesicle as a catalyst for transamination: artificial transaminase

Abstract

The non-enzymic transamination reaction of α-amino acids with α-keto acids was investigated in aqueous media at 30.0 °C. The functionalised single-walled co-vesicle composed of a synthetic peptide lipid, NN-dihexadecyl-N^α-[6-(trimethylammonio)hexanoyl]-L-histidinamide bromide, and a hydro-phobic pyridoxal derivative, 1-(NN-dihexadecylcarbamoylmethyl)-2-methyl-3-hydroxy-4-formyl-5-hydroxymethylpyridinium chloride, effectively catalysed amino-group transfer from L-phenylalanine to pyruvic acid in the presence of copper(II) ions, showing turnover behaviour. The catalytic activity of the vesicular system was much higher than those of 1,2-dimethyl-3-hydroxy-4-formyl-5-hydroxymethyl-pyridinium chloride and pyridoxal examined in aqueous media containing copper(II) ions. The rate-determining step involved in the catalytic cycle performed with the vesicular catalyst is primarily assigned to the product-releasing process, the hydrolysis of the copper(II) chelate of the aldimine Schiff's base to afford alanine.