|L-tryptophan production by the aplication of high expressed tryptophanase in Escherichia coli.
Process Biochem. 25: 172-175. 1990.
M. Terasawa, M. Fukushima, Y. Kurusu and H. Yukawa.
|A high level of expression of the tryptophanase (TPase) gene and the enzymatic formation of L-tryptophan by the application of highly expressed TPase were examined in Escherichia coli harbouring mini-F plasmid (pBR322F-tnaA), which encoded the TPase and was stably inherited at high copy number. The use of the trp promoter usually requires the addition of 3-indole acrylic acid (IA) to release partially the repression of gene expression. However, in the case of the induction of TPase gene, IA addition was not needed, since the repressor of transcription, L- tryptophan was decomposed at the early stages of cultivation by TPase allowing the expression of TPase gene to be derepressed. the specific activity of TPase in E. coli harbouring pBR322F-tna A increased by 500-fold, when compared with that of the host strain cultured under the same condition.
The enzymatic formation of L-tryptophan from indole and L-serin was examined: about one mole L-tryptophan was formed in one litre of reaction mixture at 37°C after four hours.