Purification and Properties of Phenylalanine Ammonia-lyase from Chinese Cabbage

Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), the first enzyme in the phenylpropanoid biosynthesis, catalyzes the elimination reaction of ammonium ion from L-phenylalanine. PAL was purified from the cytosolic fraction of Chinese cabbage (Brassica campestris ssp. napus var. pekinensis) through ammonium sulfate fractionation, DEAE-cellulose chromatography, Sephadex G-200 chromatography, and Q-Sepharose chromatography. It consists of four identical subunits, the molecular mass of which was estimated to be about 38,000 daltons on SDS-PAGE. The optimal pH and temperature of the purified enzyme are 8~9 and $45^{\circ}C$, respectively. Its activity is greatly inhibited by $Zn^{2+}$ ion, and strongly activated by caffeic acid. The purified PAL has some different characteristics compared to those obtained with other PALs.