Crystalline tyrosine phenol lyase was prepared from the cell extract of Erwinia herbicola grown in a medium supplemented with l-tyrosine. The crystalline enzyme was homogeneous by the criteria of ultracentrifugation and acrylamide gel electrophoresis. The molecular weight was determined to be approximately 259,000. The crystalline enzyme catalyzed the 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, 3, 4-dihydroxyphenyl-l-alanine, l- and d-serine, and l- and d-cysteine, but at lower rates than from l-tyrosine. l-Phenyl-alanine, l-alanine, phenol and pyrocatechol inhibited pyruvate formation from l-tyrosine.Crystalline tyrosine phenol lyase from Erwinia herbicola is inactive in the absence of added pyridoxal phosphate. Binding of pyridoxal phosphate to the apoenzyme is accompanied by pronounced increase in absorbance at 340 and 425 mμ. The amount of pyridoxal phosphate...