Trapping of intermediates with substrate analog HBOCoA in the polymerizations catalyzed by class III polyhydroxybutyrate (PHB) synthase from Allochromatium vinosum.

ABSTRACT: Polyhydroxybutyrate (PHB) synthases (PhaCs) catalyze the formation of biodegradable PHB polymers that are considered as an ideal alternative to petroleum-based plastics. To provide strong evidence for the preferred mechanistic model involving covalent and noncovalent intermediates, a substrate analog HBOCoA was synthesized chemoenzymatically. Substitution of sulfur in the native substrate HBCoA with an oxygen in HBOCoA enabled detection of (HB)nOCoA (n = 2-6) intermediates when the polymerization was catalyzed by wild-type (wt-)PhaECAv at 5.84 h(-1). This extremely slow rate is due to thermodynamically unfavorable steps that involve the formation of enzyme-bound PHB species (thioesters) from corresponding CoA oxoesters. Synthesized standards (HB)nOCoA (n = 2-3) were found to undergo both r

SUBMITTER: Chen C 

PROVIDER: S-EPMC4870837 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature