PURIFICATION AND PROPERTIES OF PHENYLALANINE AMMONIA-LYASE FROM LEAF MUSTARD

Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), the first enzyme in phe nylpropanoid biosynthesis, catalyzes the elimination of ammonium ion f rom L-phenylalanine. In the present study, PAL was purified through am monium sulfate fractionation, DEAE-cellulose chromatography, Sephadex G-200 chromatography, and Q-Sepharose chromatography from the cytosoli c fraction of leaf mustard (Brassica juncea var. integrifolia). It con sists of 4 subunits, each having an estimated molecular weight of abou t 40,000 on SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The opt imal pH and temperature of the purified enzyme are 9.0 and 45 degrees C, respectively. Its activity is inhibited by Zn2+ ion, and it is stro ngly activated by caffeic acid. The purified PAL seems to have some ch aracteristics different from those obtained with other PALs.