Directed Evolution of Sequence-Regulating Polyhydroxyalkanoate Synthase to Synthesize a Medium-Chain-Length-Short-Chain-Length (MCL-SCL) Block Copolymer.

Sequence-regulating polyhydroxyalkanoate synthase PhaC is a chimeric enzyme comprising PhaCs from and (). It spontaneously synthesizes a short-chain-length (SCL, ≤C) block copolymer poly(2-hydroxybutyrate)--poly(3-hydroxybutyrate) [P(2HB)--P(3HB)] from a mixture of monomer substrates. In this study, directed evolution of PhaC was performed to increase its activity toward a medium-chain-length (MCL, C) monomer, 3-hydroxyhexanoyl (3HHx)-coenzyme A (CoA).