AN ELECTROCHEMICAL CONTRIBUTION TO THE STUDY OF CATALYTIC TRANSAMINATION - SCHIFF-BASE OF PYRIDOXAL-PHOSPHATE WITH ETHYLAMINE AND ETHYLENEDIAMINE

The reactions between pyridoxal phosphate (PLP) and ethylamine (Et) an d ethylenediamine (Etd) were studied in buffered aqueous solution. The formation of Schiff bases by reversible reaction was observed in each case according to the electrochemical results. The presence of a cycl ic geminaldiamine and/or enol tautomer of the Schiff base was detected in the reaction of PLP with Etd by comparing polarographic and voltam metric results of both reactions. The increase in stability of the Sch iff base as diprotonated species, as well as the difference in which n itrogen on the Schiff base undergoes a fast protonation are associated with the presence and reduction of the enol tautomer. This implies a deviation from normal behaviour of the PLP Schiff base in aqueous solu tion. The results suggest that a very fast conversion of geminaldiamin e to Schiff base takes place at the electrode with monoprotonated and unprotonated species. The presence of a second amino group in the ethy lenediamine moiety of the Schiff base PLP-Etd essentially does not mod ify the ECE-Disp2 mechanism in strong basic media.