title: Nontemplate-dependent polymerization processes: polyhydroxyalkanoate synthases as a paradigm.
abstract: This review focuses on nontemplate-dependent polymerases that use water-soluble substrates and convert them into water-insoluble polymers that form granules or inclusions within the cell. The initial part of the review summarizes briefly the current knowledge of polymer formation catalyzed by starch and glycogen synthases, polyphosphate kinase (a polymerase), cyanophycin synthetases, and rubber synthases. Specifically, our current understanding of their mechanisms of initiation, elongation (including granule formation), termination, remodeling, and polymer reutilization will be presented. General underlying principles that govern these types of polymerization reactions will be enumerated as a paradigm for all nontemplate-dependent polymerizations. The bulk of the review then focuses on polyhydroxyalkanoate (PHA) synthases that generate polyoxoesters. These enzymes are of interest as they generate biodegradable polymers. Our current knowledge of PHA production and utilization in vitro and in vivo as well as the contribution of many proteins to these processes will be reviewed.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. stubbe@mit.edu
authors.forename: Joanne
authors.initials: J
authors.lastname: Stubbe
authors.forename: Jiamin
authors.initials: J
authors.lastname: Tian
authors.forename: Aimin
authors.initials: A
authors.lastname: He
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Sinskey
authors.forename: Adam G
authors.initials: AG
authors.lastname: Lawrence
authors.forename: Pinghua
authors.initials: P
authors.lastname: Liu
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D001426:Bacterial Proteins; D001704:Biopolymers / Q000096:biosynthesis* / Q000737:chemistry; D006003:Glycogen / Q000096:biosynthesis; D008954:Models, Biological; D008956:Models, Chemical; D010940:Plant Proteins / Q000096:biosynthesis; D011091:Polyesters / Q000378:metabolism; D011122:Polyphosphates / Q000378:metabolism; D012995:Solubility; D013213:Starch / Q000096:biosynthesis
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D010940:Plant Proteins; D011091:Polyesters; D011122:Polyphosphates; C024250:cyanophycin; D013213:Starch; D006003:Glycogen; D000217:Acyltransferases; C077225:poly(3-hydroxyalkanoic acid) synthase