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.
Kawasaki
K
K
Department of Bioscience and Chemistry, Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
Yokota
A
A
Tomita
F
F
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