The function of ackA and pta genes is necessary for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) synthesis in recombinant pha+ Escherichia coli.
In Escherichia coli carrying the poly(3-hydroxyalkanoate) (PHA) biosynthesis pathway on a plasmid (pha+), the function of the ackA (acetate kinase) and pta (phosphotransacetylase) genes is necessary for efficient incorporation of 3-hydroxyvalerate (3-HV) into the copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)). Recombinant pha+ E. coli fadR atoC(Con) strains possessing mutations in ackA, pta, or both ackA and pta exhibited substantially reduced levels of 3-HV formation. Conversely, the same strains carrying the ackA gene on a multicopy plasmid exhibited an increase in 3-HV formation concomitant with a large increase in acetate kinase activity. However, if the strain possessing the multicopy ackA+ plasmid was mutant at the pta locus, it lost the ability to incorporate significant amounts of 3-HV into P(3HB-co-3HV). In addition to the ackA pta pathway, there is an inducible activity that can also mediate the incorporation of 3-HV into P(3HB-co-3HV). This pathway is repressed by glucose and is not normally operative in P(3HB-co-3HV) production in recombinant pha+ E. coli strains that are grown using glucose as the major carbon source. It appears likely that this activity is due to an inducible acetyl-CoA synthetase that converts propionate to propionyl-CoA.
Rhie
H G
HG
Department of Biology, Kyung Hee University, Seoul, Korea.
Dennis
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D000084:Acetate Kinase / Q000235:genetics / Q000378:metabolism*; D000106:Acetate-CoA Ligase / Q000378:metabolism; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D018628:Gene Dosage; D005798:Genes, Bacterial / Q000502:physiology*; D009154:Mutation / Q000502:physiology; D010421:Pentanoic Acids / Q000378:metabolism; D010709:Phosphate Acetyltransferase / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D011091:Polyesters / Q000378:metabolism*; D000094122:Polyhydroxybutyrates
D000084:Acetate Kinase; D000106:Acetate-CoA Ligase; D010421:Pentanoic Acids; D010709:Phosphate Acetyltransferase; D011091:Polyesters; C052620:poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate); D000094122:Polyhydroxybutyrates; C013056:beta-hydroxyvaleric acid