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Appl. Environ. Microbiol., Jan 1997, 33-38, Vol 63, No. 1
M Tuchman, BS Rajagopal, MT McCann and MH Malamy
Escherichia coli strains capable of enhanced synthesis of arginine and urea
were produced by derepression of the arginine regulon and simultaneous
overexpression of the E. coli carAB and argI genes and the Bacillus
subtilis rocF gene. Plasmids expressing carAB driven by their natural
promoters were unstable. Therefore, E. coli carAB and argI genes with and
without the B. subtilis rocF gene were constructed as a single operon under
the regulation of the inducible promoter ptrc. Arginine operator sequences
(Arg boxes) from argI were also cloned into the same plasmids for titration
of the arginine repressor. Upon overexpression of these genes in E. coli
strains, very high carbamyl phosphate synthetase, ornithine
transcarbamylase, and arginase catalytic activities were achieved. The
biosynthetic capacity of these engineered bacteria when overexpressing the
arginine biosynthetic enzymes was 6- to 16-fold higher than that of
controls but only if exogenous ornithine was present (ornithine was rate
limiting). Overexpression of arginase in bacteria with a derepressed
arginine biosynthetic pathway resulted in a 13- to 20-fold increase in urea
production over that of controls with the parent vector alone; in this
situation, the availability of carbamyl phosphate was rate limiting.
Copyright © 1997, American Society for Microbiology
Enhanced production of arginine and urea by genetically engineered Escherichia coli K-12 strains
Department of Pediatrics, University of Minnesota Hospitals, Minneapolis 55455, USA.
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