EXPRESSION OF POPLAR PHENYLALANINE AMMONIA-LYASE IN INSECT-CELL CULTURES

A cDNA encoding one of the phenylalanine ammonia-lyase genes from Popu lus trichocarpa x deltoides was inserted into a baculovirus expression vector and the PAL protein was successfully expressed in insect cell cultures. High levels of active holoenzyme were obtained that could be purified in a single chromatographic step. Site-directed mutagenesis and expression of the mutant enzyme confirmed that conversion of the p utative active site serine(202) residue to alanine is sufficient to de stroy the catalytic activity of PAL.