Poly[β-hydroxybutyrate-co-β-hydroxyvalerate] co-polymer, PHBV, is a polyhydroxyalkanoate (PHA) that has greater utility as a biodegradable thermoplastic polyester than poly-β-hydroxybutyrate, PHB. In order to produce PHBV, a system of pathways is required to produce both hydroxybutyrate (HE) and hydroxyvalerate (HV) monomers from the sources of carbon. A working model for conversion of glucose to PHBV via acetyl- and propionyl-coenzyme A was constructed by expressing the PHA biosynthesis genes from Alcaligenes eutrophus in Escherichia coil strain K-12 under novel growth conditions. When 1 mM valine was added to 1% glucose medium, growth ceased and up to 2.5% of the incorporated monomers were HV; up to 4% were HV when 1 mM threonine was added as well. Threonine dehydratase (TD) converts threonine to α-ketobutyrate; TD is required for HV to be incorporated into PHA unless its transaminated reaction product, α-aminobutyrate, is added to the medium. Intracellular α-ketobutyrate accumulates when valine is added to the medium because valine, which cannot be metabolized to HV by E. coli strain K-12, stimulates TD and inhibits acetolactate synthase. In turn, α-ketobutyrate is converted to propionyl-CoA by the E. coil pyruvate dehydrogenase complex. This constitutes a defined system of pathways for synthesis of a heteropolymeric PHA from a single carbon source, which in the future could be transferred to other organisms including plants.
|Original language||English (US)|
|Number of pages||10|
|Journal||International Journal of Biological Macromolecules|
|State||Published - Aug 1996|
Bibliographical noteFunding Information:
We gratefullya cknowledgTeo m Krick and Rick Riemero f the MinnesotaA griculturaEl xperimenStt a-tion for experat ssistancwei thGC, MS, and NMR, the E. coil GeneticS tockC entear t Yale Universitfyo r pro-mptlys upplyingn eededs trains,a nd David Sherman, CarrollV ancea, ndJ ohnG ronwaldfo rc riticarl eviewo f thism anuscripTt.h is work was supportebdy the Con-sortiumfo r PlantB iotechnologRye searchIn, c., by the United States Departmenot f Energy (Grant no. OR22072S, ubcontrancto . 54 0020 820)b, y theL egisla-tive Committeeo n MinnesotaR esource(sG rantno. MNADM 02140-23953b)y, Proctora nd Gamblea, nd by the Universityo f MinnesotaT. his paperi s Min-nesotaA griculturaElx perimenStt ationP ublicatioNn o. 22091.
- Poly-β-hydroxyalkanoic acids
- Poly[β-hydroxybutyrate-co-β-hydroxyvalerate] co-polymer
- Propionyl co-enzyme A
- Pyruvate dehydrogenase
- Threonine dehydratase