Characterization of bacterial L-(-)-tyrosine decarboxylase by isoelectric focusing and gel chromatography

The purification of L-(-)-tyrosine apodecarboxylase (TAD) (E.C. 4.1.1.25), obtained from extracts of cells of Streptococcus faecalis, has been investigated by means of preparative isoelectric focusing, molecular sieve chromatography and hydrophobic interaction chromatography. Isoelectric focusing demonstrated two separate fractions possessing enzyme activity that had pI values of 4.5 and ca. 3.2. In the chromatographic methods, however, the activity was obtained in a single peak. It was found that hydrophobic interaction chromatography on phenyl-Sepharose was particularly suitable for purification purposes. The enzyme is very firmly bound to octyl-Sepharose CL-4B but retains most of its activity even in the bound state.