Tyrosine Phenol Lyase

Abstract

Abstract Crystalline l-tyrosine phenol lyase (deaminating) was prepared from the cell extract of Escherichia intermedia A-21 grown in a medium supplemented with l-tyrosine. The purification procedure included ammonium sulfate fractionation, protamine sulfate treatment, DEAE-Sephadex and hydroxylapatite column chromatographies, and Sephadex G-150 gel filtration. Crystals were obtained from solutions of the purified enzyme by the addition of ammonium sulfate. The enzyme was homogeneous by the criteria of ultracentrifugation and acrylamide gel electrophoresis. The molecular weight was determined to be approximately 170,000. The crystalline enzyme catalyzed the stoichiometric conversion of l-tyrosine into phenol, pyruvate, and ammonia, in the presence of added pyridoxal phosphate. The enzyme also catalyzed pyruvate formation from d-tyrosine, S-methyl-l-cysteine, l-cysteine, l-serine and d-serine, but at rather lower rates than from l-tyrosine. l-Alanine, phenol, and pyrocatechol inhibited pyruvate formation from these substrates.