Chain termination in polyhydroxyalkanoate synthesis: involvement of exogenous hydroxy-compounds as chain transfer agents

Madden, Leigh A.; Anderson, Angelika; Shah, Devang; Asrar, Jawed

doi:10.1016/s0141-8130(99)00014-8

Cited by 129 publications

(109 citation statements)

References 27 publications

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“…PhaC is thought to catalyze termination itself, although a phasin protein, PhaP, has been implicated in promoting the termination event (25,45,46). Proposals for the mechanism of termination include hydrolysis by a base-activated water molecule; transfer of the PHB chain to a nucleophilic residue on PhaC followed by hydrolysis; or chain transfer to an exogenous thiol-or hydroxyl-containing molecule (22,(47)(48)(49). Following chain termination and release of the polymer, it has been shown that the class III PhaC remains loaded with 3-10 HB units, suggesting that chain termination occurs at a site distant from the active site (47).…”

Section: Journal Of Biological Chemistry 25271mentioning

confidence: 99%

Structure of the Catalytic Domain of the Class I Polyhydroxybutyrate Synthase from Cupriavidus necator

Wittenborn¹,

Jost²,

Wei³

et al. 2016

Journal of Biological Chemistry

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Edited by F. Peter GuengerichPolyhydroxybutyrate synthase (PhaC) catalyzes the polymerization of 3-(R)-hydroxybutyryl-coenzyme A as a means of carbon storage in many bacteria. The resulting polymers can be used to make biodegradable materials with properties similar to those of thermoplastics and are an environmentally friendly alternative to traditional petroleum-based plastics. A full biochemical and mechanistic understanding of this process has been hindered in part by a lack of structural information on PhaC. Here we present the first structure of the catalytic domain (residues 201-589) of the class I PhaC from Cupriavidus necator (formerly Ralstonia eutropha) to 1.80 Å resolution. We observe a symmetrical dimeric architecture in which the active site of each monomer is separated from the other by ϳ33 Å across an extensive dimer interface, suggesting a mechanism in which polyhydroxybutyrate biosynthesis occurs at a single active site. The structure additionally highlights key side chain interactions within the active site that play likely roles in facilitating catalysis, leading to the proposal of a modified mechanistic scheme involving two distinct roles for the active site histidine. We also identify putative substrate entrance and product egress routes within the enzyme, which are discussed in the context of previously reported biochemical observations. Our structure lays a foundation for further biochemical and structural characterization of PhaC, which could assist in engineering efforts for the production of eco-friendly materials.

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Section: Journal Of Biological Chemistry 25271mentioning

confidence: 99%

Structure of the Catalytic Domain of the Class I Polyhydroxybutyrate Synthase from Cupriavidus necator

Wittenborn¹,

Jost²,

Wei³

et al. 2016

Journal of Biological Chemistry

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“…With the addition of exogenous chain transfer agents with hydroxyl end groups such as glycerol and low molecular weight polyethylene glycol derivatives (PEG), PHA polymerization can be terminated early. 101,102 Since glycerol contains three hydroxyl groups per molecule and is much smaller than the PEG derivatives, it makes a good candidate as a chain transfer agent. By varying the concentration of glycerol in the starting media the molecular weight of PHAs can be controlled, due to the prevalence of glycerol terminating the PHA synthesis.…”

Section: Production and Characterization Of Polyhydrox-yalkanoates Frmentioning

confidence: 99%

Bioplastics from waste glycerol derived from biodiesel industry

Zhu

Chiu

Nakas

et al. 2013

J of Applied Polymer Sci

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Polyhydroxyalkanoates (PHAs) are polyesters that can be biologically synthesized by many microorganisms and engineered plants that have been investigated by microbiologists, biochemists, polymer scientists, material engineers, and medical researchers for several decades. Research on microbial production of PHAs has been extensively focused on using pure carbon sources, such as sugars and fatty acids. Practical considerations of production costs of PHAs have resulted in research efforts to use alternative renewable and inexpensive feedstocks. One potential feedstock for the production of PHA polymers is the glycerol waste byproduct of biodiesel production. The major focus of this review is the production of PHA polymers from glycerol. A review of biosynthetic pathways for PHAs production from glycerol, current production of waste glycerol in biodiesel industry, physical and mechanical properties of PHAs, and applications of PHAs in the areas of packaging industry, implant materials, drug carrier, biofuels, are covered.

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“…In Methylobacterium extorquens and C. necator, PHB obtained from glycerol, ethanol, or methanol had a lower molecular mass than that obtained from other substrates (such as succinate, glucose, and fructose), and the molecular mass of the polymer was shown to decrease with increasing glycerol concentrations (23). This effect was further analyzed and attributed to chain termination caused by glycerol (10). In studies performed using Pseudomonas strains, increasing glycerol concentrations (from 1% [wt/ vol] to 5% [wt/vol]) resulted in a decrease of more than 50% in the M r of the PHB produced by P. oleovorans and mediumchain-length PHA synthesized by P. corrugata (2).…”

mentioning

confidence: 99%

“…Glycerol has also been used for PHB synthesis in recombinant E. coli (12,15). PHAs obtained from glycerol were reported to have a significantly lower molecular weight than polymer synthesized from other substrates, such as glucose or lactose (10,23).…”

mentioning

confidence: 99%

Effects of Aeration on the Synthesis of Poly(3-Hydroxybutyrate) from Glycerol and Glucose in Recombinant Escherichia coli

Almeida

Giordano

Nikel

et al. 2010

Appl Environ Microbiol

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Bioreactor cultures of Escherichia coli recombinants carrying phaBAC and phaP of Azotobacter sp. FA8 grown on glycerol under low-agitation conditions accumulated more poly(3-hydroxybutyrate) (PHB) and ethanol than at high agitation, while in glucose cultures, low agitation led to a decrease in PHB formation. Cells produced smaller amounts of acids from glycerol than from glucose. Glycerol batch cultures stirred at 125 rpm accumulated, in 24 h, 30.1% (wt/wt) PHB with a relative molecular mass of 1.9 MDa, close to that of PHB obtained using glucose.

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Chain termination in polyhydroxyalkanoate synthesis: involvement of exogenous hydroxy-compounds as chain transfer agents

Cited by 129 publications

References 27 publications

Structure of the Catalytic Domain of the Class I Polyhydroxybutyrate Synthase from Cupriavidus necator

Structure of the Catalytic Domain of the Class I Polyhydroxybutyrate Synthase from Cupriavidus necator

Bioplastics from waste glycerol derived from biodiesel industry

Effects of Aeration on the Synthesis of Poly(3-Hydroxybutyrate) from Glycerol and Glucose in Recombinant Escherichia coli

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