Enzymatic synthesis of L-tryptophan by Enterobacter aerogenes tryptophanase highly expressed in Escherichia coli, and some properties of the purified enzyme.
We constructed two plasmids that have a strong tac promoter and a structural gene for tryptophanase of Enterobacter aerogenes SM-18 (pKT901EA) or Escherichia coli K-12 (pKT951EC). The tryptophanase activity of E. coli JM109 transformed with pKT901EA (JM109/pKT901EA) was inducible with isopropyl-beta-D-thiogalactopyranoside, and 3.6 times higher than that of E. aerogenes SM-18. Cells of JM109/pKT901EA induced for tryptophanase synthesized L-tryptophan from indole, ammonia, and pyruvate more efficiently than E. aerogenes SM-18. Although JM109/pKT951EC expressed a similar level of tryptophanase activity to that of JM109/pKT901EA, the synthesis of L-tryptophan by the cells of JM109/pKT951EC did not proceed well compared with JM109/pKT901EA. Tryptophanases from E. aerogenes and E. coli K-12 were purified, and their properties were investigated. The purified E. aerogenes tryptophanase showed higher stability against heat inactivation than E. coli tryptophanase.
Department of Bioscience and Chemistry, Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
K
K
Kawasaki
A
A
Yokota
F
F
Tomita
D004754:Enterobacter / Q000201:enzymology*; D004790:Enzyme Induction; D004926:Escherichia coli; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D014364:Tryptophan / Q000096:biosynthesis*; D014368:Tryptophanase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
D011994:Recombinant Proteins; D014364:Tryptophan; D014368:Tryptophanase