PHAs are a family of microbial polyesters that have captivated most courtesy as biodegradable and biocompatible plastics and elastomers that can surrogate petrochemical counterparts. There have been countless papers and patents on gene cloning and metabolic engineering of PHA biosynthetic machineries, biochemical studies, and prolongation of PHAs; elementary Google hunt with “polyhydroxyalkanoates” yielded earnings of 223,000 request pages. PHAs have always been deliberate extraordinary examples of biological polymer synthesis. It is strange to see PHAs of 500 kDa to infrequently as high as 10,000 kDa can be synthesized in vivo by PHA synthase, a pivotal polymerizing enzyme in PHA biosynthesis. They have captivated good seductiveness in final a clear structure of PHA synthase over a final 30 years, though unfortunately though success. Thus, a characteristics and molecular mechanisms of PHA synthase were underneath a dim veil.
In dual papers published back-to-back in Biotechnology Journal online on Nov 30, 2016, a Korean investigate group led by Professor Kyung-Jin Kim during Kyungpook National University and Distinguished Professor Sang Yup Lee during a Korea Advanced Institute of Science and Technology (KAIST) described a clear structure of PHA synthase from Ralstonia eutropha, a best complicated micro-organism for PHA production, and reported a constructional basement for a minute molecular mechanisms of PHA biosynthesis. The clear structure has been deposited to Protein Data Bank in Feb 2016. After deciphering a clear structure of a catalytic domain of PHA synthase, in further to other constructional studies on whole enzyme and associated proteins, a investigate group also achieved experiments to clarify a mechanisms of a enzyme reaction, validating minute structures, enzyme engineering, and also N-terminal domain studies among others.
Through several biochemical studies formed on clear structure, a authors uncover that PHA synthase exists as a dimer and is divided into dual graphic domains, a N-terminal domain (RePhaC1ND) and a C-terminal domain (RePhaC1CD). The RePhaC1CD catalyzes a polymerization greeting around a non-processive ping-pong resource regulating a Cys-His-Asp catalytic triad. The dual catalytic sites of a RePhaC1CD dimer are positioned 33.4 Å apart, suggesting that a polymerization greeting occurs exclusively during any site. This investigate also presents a structure-based mechanisms for substrate specificities of several PHA synthases from opposite classes.
Professor Sang Yup Lee, who has worked on this subject for some-more than 20 years, pronounced “The formula and information presented in these dual papers have prolonged been awaited not usually in a PHA community, though also metabolic engineering, bacteriology/microbiology, and in ubiquitous biological sciences communities. The constructional information on PHA synthase together with a recently deciphered greeting mechanisms will be profitable for bargain a minute mechanisms of biosynthesizing this critical energy/redox storage material, and also for a receptive engineering of PHA synthases to furnish engineer bioplastics from several monomers some-more efficiently.”
Indeed, these dual papers published in Biotechnology Journal finally exhibit a 30-year poser of machine of biological polyester synthesis, and will offer as a essential compass in formulating engineer and some-more fit bioplastic machineries.
