Co-expression of trpBA and serA Genes in Escherichia coli

Abstract:

Escherichia coli trpBA-encoded tryptophan synthetase (TSase) and serA-encoded D-3-pho- sphoglycerate dehydrogenase (PGDH) are key enzymes in tryptophan and serine biosynthesis pathway, respectively. In order to improve bio-production of tryptophan through bioengineering means, a feedback inhibition resistant serA gene was cloned by PCR and co-expressed with trpBA gene, which was cloned and expressed before. Four recombinant plasmids were constructed successfully in the recombinant strains. SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) showed target protein products of 37 kD (PGDH), 29 kD (TSase α subunit), 44 kD (TSase β subunit). The enzyme activity analysis indicated the specific activities of TSase was increased by 2~4-fold, and that of PGDH was increased by 2.1~3.6-fold, compared to the control. High enzyme activities could lead to high tryptophan production by the shake flask fermentation. The amount of tryptophan biosynthesis in ABA-I strain was increased by 20.2 folds compared with that of the host strains.