Purification and characterization of tyrosine decarboxylase of Lactobacillus brevis IOEB 9809 isolated from wine

Tyrosine decarboxylase (EC 4.1.1.25) (TDC) from the wine Lactobacillus brev is is IOEB 9809 was purified by a rapid procedure involving anion exchange chromatography, ultrafiltration and hydrophobic interaction chromatography. The protein comprised two subunits of identical molecular mass (approximat elly 70 000 Da). Enzyme activity was dependent on exogenously supplied pyri dosal 5'-phosphate and the enzyme was stable at 4 degreesC in the presence or the coenzyme. Optimum pH for the purr enzyme was 5.0. At this pH. TDC ex hibited Michaelis-Menten kinetics (K-m 0.63 mM, V-max 998 units) and uas hi ghly substrate-specific for L-tyrosine. Other amino acids and L-DOPA are no t converted by the protein. Tyramine acted as a mixed non-competitive inhib itor. Significant similarities in some biochemical properties were observed with the corresponding decarboxylase enzyme or Streptococcus faecalis, the sole bacterial TDC described to date. (C) 2001 Federation of European Micr obiological Societies. published by Elsevier Science B.V. All rights reserv ed.