Racemization of D- or L-alanine by crystalline tyrosine phenol-lyase from Eshherichia intermedia

Abstract

Conversion of D- or L-alanine into the racemate is catalyzed by crystalline tyrosine phenol-lyase prepared from cells of Escherichia intermedia . The racemization reaction proceeds optimally at pH 7.2–7.5, as a function of enzyme concentration and incubation time. The Km for L-alanine and the maximal velocity of racemization are 2.6 × 10 −2 M and 0.051 μmole/minute/mg of protein, respectively. Addition of either D- or L-alanine to holotyrosine phenol-lyase results in the appearance of a new spectral band near 500 mμ which has been ascribed to the intermediates in many pyridoxal dependent reactions.