Evolution of propanediol utilization in Escherichia coli: mutant with improved substrate-scavenging power.
AUTOR(ES)
Hacking, A J
RESUMO
Wild-type strains of Escherichia coli are unable to use L-1,2-propanediol as a carbon and energy source. A series of mutants, able to grow on this compound at progressively faster rates, had been isolated by repeated transfers to a medium containing 20 mM L-1,2-propanediol. These strains synthesize at high constitutive levels a propanediolmicotinamide adenine dinucleotide oxidoreductase, an enzyme serving as a lactaldehyde during L-fucose fermentation by wild type cells. In this study, a mutant that can grow rapidly on the novel carbon source was subjected to further selection in a medium containing L-1,2-propanediol never exceeding 0.5 mM to obtain a derivative that has an increased power to extract the substrate from the medium. The emerging mutant exhibited four changes at the enzymatic level: (i) fuculose 1-phosphate aldolase activity is lost; (ii) the constitutive propanediol oxidoreductase activity is increased in its level; (iii) lactaldehyde dehydrogenase becomes constitutive and shows an elevated specific activity in crude extracts; and (iv) at low concentrations of propanediol, the facilitated diffusion across the cell membrane is enhanced. Changes two to four seem to act in concert in the trapping of propanediol by hastening its rate of entry and conversion to an ionized metabolite, lactate.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=218575Documentos Relacionados
- Rhamnose-induced propanediol oxidoreductase in Escherichia coli: purification, properties, and comparison with the fucose-induced enzyme.
- Metabolism of L-fucose and L-rhamnose in Escherichia coli: differences in induction of propanediol oxidoreductase.
- Regulatory changes in the fucose system associated with the evolution of a catabolic pathway for propanediol in Escherichia coli.
- Lactose permease of Escherichia coli: properties of mutants defective in substrate translocation.
- Control of Mixed-Substrate Utilization in Continuous Cultures of Escherichia coli