Novel direct synthesis of l-phenylalanine methyl ester by using Rhodotorula glutinis phenylalanine ammonia lyase in an organic-aqueous biphasic system

Abstract

A procedure for the direct, one-step enzymatic conversion of trans-cinnamyl methyl ester to L-phenylalanine methyl ester is described. The reverse reaction of phenylalanine ammonia lyase from Rhodotorula glutinis was utilized for this conversion. Insolubility of substrate trans-cinnamyl methyl ester in aqueous buffer solution was overcome by employing an organic-aqueous biphasic system, heptane:0.1 m Tris-sulfate buffer, pH 9.0 (2:1). Different conditions were optimized for the maximal conversion such as time (16–18 h), temperature (30°C), pH (9.0), concentration of substrates, 0.1 m trans-cinnamyl methyl ester and 1 m (NH 4) 2 SO 4, and nature of the organic solvent (heptane); about 70% conversion of substrate to product was obtained under these conditions. Formation of the product, l-phenylalanine methyl ester, was identified by paper chromatography and was further confirmed by autoradiography and NMR spectral analyses.