Abstract：Phenylalanine ammonia-lyase(PAL) is widespread in plant as the first key enzyme of phenylpropanoid pathway, it can be used to produce L-phenylalanine (L-Phe) through its reverse catalytic activity in biochemical industry. Nowadays, it is an important way to screen the PAL sources with high activity and stability for increasing the yield of L-Phe. In this study, a phenylalanine ammonia-lyase gene from Fagopyrum tatarcium(FtPAL) was constructed to pET-30b(+) and expressed in E.coli BL21(DE3), target protein FtPAL's reverse catalyze properties was characterized after purification. The results showed that FtPAL arrived at the highest forward catalytic activity 24.17 U/mg after induction of 5 h. Furthermore, the forward and reverse catalytic activities of purified FtPAL were 158.74 U/mg and 194.11 U/mg, respectively. Meanwhile, thin-layer chromatography(TLC) analysis also indicated FtPAL has the ability to catalyze trans-cinnamic acid into L-Phe. FtPAL was most active at 30 ℃ and pH 10, and showed the low thermal stability and moderate pH stability. FtPAL activity was activated by Mg2+ ion (P＜0.01), but was inhibited by other metal ions (Na+、Mn2+、Fe2+、Fe3+、Cu2+ and Ca2+) (P＜0.05 or P＜0.01). Particularly, Hg2+ could make FtPAL lose activity completely. Our study not only proves FtPAL has the activity to synthesize L-Phe, but also lays the foundation for improving its catalytic efficiency and stability through the genetic engineering.
