Novel interpretations of in vitro polyhydroxyalkanoate polymerization phenomena

Polyhydroxyalkanoates (PHAs) are gaining popularity as a viable biological alternative to petroleum-derived polyolefin plastic materials, especially because their material properties can be tuned through monomer composition and configuration, an uncommon phenomena in enzymatic polymer products. Because the native function of these polymers is chemical energy storage, the metabolic synthesis routes can vary dramatically from one microorganism to the next, save one crucial enzyme – the PHA synthase, responsible for the direct polymerization and composition of PHAs. For this reason, the field of PHA synthase mechanics is blooming as more variants of this enzyme are discovered. However, due to the complexity associated with this surface-driven micelle growth reaction, the initial reaction conditions dictate a variety of observed behaviors during in vitro kinetic analysis. In this work, we discuss the importance of these initial conditions and their associated behaviors and propose minimal kinetic models to help elucidate the significant mechanics of this complex in vitro reaction. The theory and inferences of this work provide a more complete understanding of in vitro PHA synthesis and aid in the design of future in vitro PHA synthase enzymatic assays. [Display omitted] •Impact of initial conditions on observed reaction behavior is discussed.•A brief examination of previous kinetic studies is documented.•Rationalization of contradictory observations from literature is reported.•Kinetic models are proposed to elucidate significant reaction mechanics.•Models derived herein convincingly fit data from literature.