Τοwards a Synthetic Tryptophan Aminotransferase

Sammanfattning: The synthesis and evaluation of a molecularly imprinted polymer has been undertaken using an oxazine-based tryptophanamide transition state analogue (TSA) as template. An efficient route to the synthesis of oxazine-based TSAs for the reaction of pyridoxamine and indole-3-pyruvic acid has been established, with yields of up to 80%. NMR titration studies were performed to examine the interactions between the functional monomer, methacrylic acid and the template. Complexation of the template by functional monomer in the presence of crosslinker showed an apparent KD of 0.63-0.79 ± 0.04 M (293 K, acetonitrile-d3) based upon the chemical shift of the template amide protons. TSA-imprinted and non-imprinted reference polymers were synthesized by free radical polymerization in acetonitrile. Polymer monoliths were ground and fractionated into a 25-63 μm size range. Polymer-ligand recognition studies were conducted using the polymers as HPLC stationary phases. An imprinting factor (IF) of 2.93 was observed for the TSA, indicating the selectivity of the imprinted sites for the template. Studies using the D- and L-enantiomers of the phenylalaninamide analogue of the template showed enantioselectivity in the case of the imprinted polymer, α = 1.10, though not in the case of the non-imprinted reference polymer (1.00). Using UV-spectroscopy based polymer-ligand binding studies, a maximum theoretical capacity (Bmax) of 0.059 ± 0.004 mmol·g-1 was observed for the imprinted polymer. Conclusively, an imprinted polymer with binding sites selective for the TSA was successfully prepared and shall subsequently be studied with respect to its capacity to catalyse the transamination reaction between pyridoxamine and indole-3-pyruvic acid to yield pyridoxal and tryptophan.