title: In vitro evidence of chain transfer to tetraethylene glycols in enzymatic polymerization of polyhydroxyalkanoate.
abstract: A polyhydroxyalkanoate (PHA) was enzymatically synthesized in vitro, and the end structure of PHA associated with a chain transfer (CT) reaction was investigated. In the CT reaction, PHA chain transfers from PHA synthase (PhaC) to a CT agent, resulting in covalent bonding of CT agent to the PHA chain at its carboxyl end. In vitro CT reaction has never been demonstrated because of relatively low yields of in vitro synthesized poly[(R)-3-hydroxybutyrate)] (P(3HB)), which makes it difficult to characterize the end structures of the polymers by nuclear magnetic resonance (NMR). To overcome these difficulties, a novel in vitro synthesis method that produced relatively larger amounts of P(3HB) was developed by employing PhaCDa from Delftia acidovorans and two enantioselective enoyl-coenzyme A (CoA) hydratases which were R-hydratase (PhaJAc) from Aeromonas caviae and S-hydratase (FadB1x) from Pseudomonas putida KT2440 with β-butyrolactone and CoA as starting materials. Using this method, P(3HB) synthesis was performed with tetraethylene glycols (TEGs) as a discriminable CT agent, and the resultant P(3HB) was characterized by (1)H-NMR. NMR analysis revealed that the carboxylic end of P(3HB) was covalently linked to TEGs, providing the first direct evidence of in vitro CT reaction.
authors.affiliation: Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan. satoshi.tomizawa@riken.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tomizawa
authors.forename: Shun
authors.initials: S
authors.lastname: Sato
authors.forename: John Chi-Wei
authors.initials: JC
authors.lastname: Lan
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Hideki
authors.initials: H
authors.lastname: Abe
authors.forename: Takeharu
authors.initials: T
authors.lastname: Tsuge
mesh_terms: D000217:Acyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D057585:Aeromonas caviae / Q000201:enzymology*; D020605:Delftia acidovorans / Q000201:enzymology*; D004746:Enoyl-CoA Hydratase / Q000302:isolation & purification / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000378:metabolism*; D054813:Polyhydroxyalkanoates / Q000378:metabolism*; D058105:Polymerization; D016958:Pseudomonas putida / Q000201:enzymology*
chemical_list: D054813:Polyhydroxyalkanoates; D011092:Polyethylene Glycols; D000217:Acyltransferases; C077225:poly(3-hydroxyalkanoic acid) synthase; D004746:Enoyl-CoA Hydratase