Title : Polyester synthases: natural catalysts for plastics - Rehm_2003_Biochem.J_376_15
Author(s) : Rehm BH
Ref : Biochemical Journal , 376 :15 , 2003
Abstract :

Polyhydroxyalkanoates (PHAs) are biopolyesters composed of hydroxy fatty acids, which represent a complex class of storage polyesters. They are synthesized by a wide range of different Gram-positive and Gram-negative bacteria, as well as by some Archaea, and are deposited as insoluble cytoplasmic inclusions. Polyester synthases are the key enzymes of polyester biosynthesis and catalyse the conversion of (R)-hydroxyacyl-CoA thioesters to polyesters with the concomitant release of CoA. These soluble enzymes turn into amphipathic enzymes upon covalent catalysis of polyester-chain formation. A self-assembly process is initiated resulting in the formation of insoluble cytoplasmic inclusions with a phospholipid monolayer and covalently attached polyester synthases at the surface. Surface-attached polyester synthases show a marked increase in enzyme activity. These polyester synthases have only recently been biochemically characterized. An overview of these recent findings is provided. At present, 59 polyester synthase structural genes from 45 different bacteria have been cloned and the nucleotide sequences have been obtained. The multiple alignment of the primary structures of these polyester synthases show an overall identity of 8-96% with only eight strictly conserved amino acid residues. Polyester synthases can been assigned to four classes based on their substrate specificity and subunit composition. The current knowledge on the organization of the polyester synthase genes, and other genes encoding proteins related to PHA metabolism, is compiled. In addition, the primary structures of the 59 PHA synthases are aligned and analysed with respect to highly conserved amino acids, and biochemical features of polyester synthases are described. The proposed catalytic mechanism based on similarities to alpha/beta-hydrolases and mutational analysis is discussed. Different threading algorithms suggest that polyester synthases belong to the alpha/beta-hydrolase superfamily, with a conserved cysteine residue as catalytic nucleophile. This review provides a survey of the known biochemical features of these unique enzymes and their proposed catalytic mechanism.

PubMedSearch : Rehm_2003_Biochem.J_376_15
PubMedID: 12954080

Related information

Substrate 3HB-CoA
Family 3HB-CoA    PHA_synth_I    PHA_synth_II    PHA_synth_III_C    PhaC_cen_dom

Citations formats

Rehm BH (2003)
Polyester synthases: natural catalysts for plastics
Biochemical Journal 376 :15

Rehm BH (2003)
Biochemical Journal 376 :15