Metabolism of Aromatic Amino Acid in Microorganisms

Abstract

Phenylalanine ammonia-lyase, which catalyzes the conversion of L-phenylalanine to trans-cinnamic acid and ammonia, has been partially purified from the cells of Rhodotorula. Some of the properties of this phenylalanine ammoyia-lyase were investigated. The enzyme was stable in phosphate buffer of pH over the range of 6.0 to 7.0 On heating, the enzyme was stable up to 50°C, but above 60°C, it was destroyed. The enzyme activity was strongly inhibited by p-chloromercuribenzoate at 10-5M and almost recovered by the addition of glutathione or mercaptoethanol at 10-3M. The present enzyme preparation of Rhodotorula also catalyzed the deamination of L-tyrosine to trans-p-coumaric acid. trans-p-Coumaric acid was isolated from the reaction mixture and identified by its absorption spectra. The rates of deamination showed optima at pH 9.0 and 9.5 for L-phenylalanine and L-tyrosine, respectively.