EXPRESSION OF RECOMBINANT L-PHENYLALANINE AMMONIA-LYASE IN ESCHERICHIA COLI

The pal gene coding for L-phenylalanine ammonia-lyase of Rhodosporidium toruloides (GenBank entry no. X12702.1) with optimized sequence was cloned into an expressing vector pET28a. Three parameters of expression (inductor type, duration, and temperature of induction) were optimized, which resulted in a strain producing recombinant L-phenylalanine ammonia-lyase with the maximal productivity, that is, 35 ± 1% to total cell protein, upon utilization of 0.2% lactose (according to Studier) induction during 18 h at 37°C. The recombinant L-phenylalanine ammonia-lyase was found to be insoluble by 99%. Solubility of the protein did not improve upon utilization of 1 mM IPTG as an inductor instead of 0.2% lactose, or upon bacterium cultivation at various temperatures, that is 25°C and 37°C.