Chemistry Reference
In-Depth Information
CoA
OH
O
RO
RO
+
O
O
SCoA
R
n+1
n
Fig. 2
Reaction catalyzed by polyester synthase
Fig. 3
Metabolic routes towards biopolyester synthesis.
Dashed lines
represent engineered
biosynthesis routes.
Triangles
depict targets for inhibitors enabling biopolyester synthesis. En-
zymes indicated on
shaded boxes on solid lines
are biopolyester biosynthesis enzymes. With kind
permission from Springer Science+Business Media [
7
]
Reported efforts on engineering the PHA synthase towards better performance
and selectivity in vivo and in vitro were recently assessed in an excellent mini-
review by Nomura and Taguchi [
6
].
PHA polymers can be divided into three main classes with properties that are de-
pendent on their monomer composition. Short-chain-length PHAs have monomers
consisting of three to five carbons, are thermoplastic in nature, and generally lack
toughness. Medium-chain-length PHAs have monomers consisting of 6-14 carbons
and these polymers are elastomeric in nature. The third main class of PHAs includes
copolymers made up of short-chain-length and medium-chain-length HA monomers
consisting of 3-14 carbons. These PHAs have properties in between those of the first
two classes, depending on the mole ratio of monomers, and therefore have a wide
range of physical and thermal properties.
Figure
3
shows parts of the in vivo metabolic route towards PHAs. The biosyn-
thesis of poly(3-hydroxybutyric acid) (P3HB) requires the condensation of two
