Unveiling the 30-year mystery of polyhydroxyalkanoate (PHA) synthase.

Abstract

See accompanying articles by Jieun Kim et al. DOI 10.1002/biot.201600648 & Yeo-Jin Kim et al. DOI 10.1002/biot.201600649 It has been my great pleasure to read the two papers entitled ”Crystal structure of Ralstonia eutropha polyhydroxyalkanoate synthase C-terminal domain and reaction mechanisms“ by Kim et al. 1, and ”Structure and function of the N-terminal domain of Ralstonia eutropha polyhydroxyalkanoate synthase, and the proposed structure and mechanisms of the whole enzyme“ by Kim et al. 2. Polyhydroxyalkanoates (PHAs) are diverse biopolyesters accumulated by many bacteria as energy and carbon storage materials. PHAs have been exploited as biodegradable and biocompatible thermal plastics (also called Bioplastics). PHA synthase plays important roles in determining the general characteristics of PHAs produced, including molecular weight, polydispersity, monomer composition, and productivity. Global efforts have been made to understand PHA synthase via revealing its crystal structure (short as PhaC) without success over the last 30 years; however, Prof. Sang Yup Lee and his colleagues unveil the mystery in these two studies. Kim et al. 1 firstly demonstrate the crystal structure of PHA synthase from Ralstonia eutropha, the best studied bacterium for PHA production, and report the structural basis for the detailed molecular mechanisms of PHA biosynthesis. Kim et al. 2 then for the first time report the 3D reconstructed model of full length PHA synthase from R. eutropha, and performed several biochemical studies. These two studies provide feasibility for rational engineering of PHA synthase toward more efficient production of bioplastics, more broad PHA structure diversity and possibly controllable PHA molecular weights. If the mechanism is better understood, we may even be able to develop artificial synthases for synthesis of other non-PHA polyesters. With the PHA synthase structure revealed now, we are moving more close to tailor-made PHA to meet various needs. The author declares no financial or commercial conflict of interest.