Construction of co-expression SHMT and TPase recombinant vector and dual-enzymatic synthesis of L-tryptophan.
- Author:
Xin LI
1
;
Jun LIU
;
Qinqin ZHAO
;
Aicai XU
Author Information
1. College of Biological and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan 430023, China.
- Publication Type:Journal Article
- MeSH:
Escherichia coli;
enzymology;
genetics;
metabolism;
Gene Expression Regulation, Bacterial;
physiology;
Gene Expression Regulation, Enzymologic;
physiology;
Genetic Vectors;
genetics;
Glycine Hydroxymethyltransferase;
biosynthesis;
genetics;
Plasmids;
genetics;
Recombinant Fusion Proteins;
biosynthesis;
genetics;
pharmacology;
Recombination, Genetic;
genetics;
Tryptophan;
biosynthesis;
Tryptophanase;
biosynthesis;
genetics
- From:
Chinese Journal of Biotechnology
2010;26(9):1302-1308
- CountryChina
- Language:Chinese
-
Abstract:
Hydroxymethyltransferase (SHMT) and tryptophanase (TPase) are key enzymes in biosynthesis of L-tryptophan. We constructed three recombinant plasmids, including pET-SHMT, pET-TPase, and pET-ST for over-expression or co-expression of SHMT and TPase in Escherichia coli BL21 (DE3). The SDS-PAGE analysis showed that the recombinant proteins of 47 kDa and 50 kDa were expressed of pET-SHMT and pET-TPase, respectively. As compared to the host stain, the enzyme activity of SHMT and TPase was increased by 6.4 and 8.4 folds, respectively. Co-expression of both recombinant proteins, 47 kDa and 50 kDa, was also successful by using pET-ST and the enzyme activities were enhanced by 6.1 and 6.9 folds. We designed two pathways of dual-enzymatic synthesis of L-tryptophan by using these recombinant strains as source of SHMT and TPase. In the first pathway, the pET-SHMT carrying strain was used to catalyze synthesis of L-serine, which was further transformed into L-tryptophan by the pET-TPase expressing strain. These two steps sequentially took place in different bioreactors. In the second pathway, the pET-ST carrying strain, in which two enzymes were co-expressed, was used to catalyze simultaneously two steps in a single bioreactor. HPLC analysis indicated a high yield of 41.5 g/L of L-tryptophan was achieved in the first pathway, while a lower yield of 28.9 g/L was observed in the second pathway. In the first pathway, the calculated conversion rates for L-glycine and indole were 83.3% and 92.5%, respectively. In the second pathway, a comparable conversion rate, 82.7%, was achieved for L-glycine, while conversion of indole was much lower, only 82.9%.
