Partial purification and characterization of l-histidine decarboxylase from fetal rats

Abstract

Histidine decarboxylase ( l-histidine decarboxylase, EC4.1.1.22) was puriified more than 2500-fold from fetal rats. This is the first report of purification of mammalian histidine decarboxylase by modern biochemical techniques. The purification procedure consisted of ammonium sulfate fractionation, phosphoand DEAE-cellulose column chromatographies, Bio-Gel A-0.5m gel filtration, affinity chromatography using carnosine-coated agarose and Sephadex G-100 gel filtration. The purified enzyme was extremely unstable. DOPA-decarboxylase ( l-3, 4-dihydroxyphenylalanine decarboxylase, EC 4.1.1.26) activity was removed during each step of the purification procedure. Pyridoxal 5'-phosphate was required for activity. As reported earlier for crude enzyme preparations, the pH value of the incubation medium influenced the K m and V max values of the purified enzyme. It was found that ionic strength also affected these parameters.