The purification and characterization of intracellular tyrosine phenol lyase from Citrobacter freundii has been carried out. The enzyme was purified 35-fold to homogeneity by ammonium sulphate precipitation and hydrophobic interaction chromatography. Its subunit molecular weight was found to be 52 kDa on sodium dodecyl sulphate polyacrylamide gel electrophoresis. The purified tyrosine phenol lyase showed maximum activity in borate buffer (0.05 M at pH 8.5) at 45 A degrees C after 20 min of incubation. The K (m) and V (max) values of purified enzyme were found to be 0.446 mm and 0.342 mM/min/mg. This enzyme exhibits t (1/2) of 10, 52 and 130 min at 55, 45 and 35 A degrees C, respectively. The N-terminal amino acid sequence was determined as MET-ASN-TYR-PRO-ALA-GLU-PRO-PHE-ARG-ILE-TRP-TRP-VAL-GLY.