Isolated Poly(3-Hydroxybutyrate) (PHB) Granules Are Complex Bacterial Organelles Catalyzing Formation of PHB from Acetyl Coenzyme A (CoA) and Degradation of PHB to Acetyl-CoA
- 15 November 2007
- journal article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 189 (22), 8250-8256
- https://doi.org/10.1128/jb.00752-07
Abstract
Poly(3-hydroxybutyrate) (PHB) granules isolated in native form (nPHB granules) from Ralstonia eutropha catalyzed formation of PHB from 14 C-labeled acetyl coenzyme A (CoA) in the presence of NADPH and concomitantly released CoA, revealing that PHB biosynthetic proteins (acetoacetyl-CoA thiolase, acetoacetyl-CoA reductase, and PHB synthase) are present and active in isolated nPHB granules in vitro. nPHB granules also catalyzed thiolytic cleavage of PHB in the presence of added CoA, resulting in synthesis of 3-hydroxybutyryl-CoA (3HB-CoA) from PHB. Synthesis of 3HB-CoA was also shown by incubation of artificial (protein-free) PHB with CoA and PhaZa1, confirming that PhaZa1 is a PHB depolymerase catalyzing the thiolysis reaction. Acetyl-CoA was the major product detectable after incubation of nPHB granules in the presence of NAD + , indicating that downstream mobilizing enzyme activities were also present and active in isolated nPHB granules. We propose that intracellular concentrations of key metabolites (CoA, acetyl-CoA, 3HB-CoA, NAD + /NADH) determine whether a cell accumulates or degrades PHB. Since the degradation product of PHB is 3HB-CoA, the cells do not waste energy by synthesis and degradation of PHB. Thus, our results explain the frequent finding of simultaneous synthesis and breakdown of PHB.Keywords
This publication has 54 references indexed in Scilit:
- Poly(3-Hydroxybutyrate) Granules at the Early Stages of Formation Are Localized Close to the Cytoplasmic Membrane in Caryophanon latumApplied and Environmental Microbiology, 2007
- Studies on the Influence of Phasins on Accumulation and Degradation of PHB and Nanostructure of PHB Granules inRalstoniaeutrophaH16Biomacromolecules, 2006
- Genome sequence of the bioplastic-producing “Knallgas” bacterium Ralstonia eutropha H16Nature Biotechnology, 2006
- Assay of Poly(3-Hydroxybutyrate) Depolymerase Activity and Product DeterminationApplied and Environmental Microbiology, 2006
- NONTEMPLATE-DEPENDENT POLYMERIZATION PROCESSES: Polyhydroxyalkanoate Synthases as a ParadigmAnnual Review of Biochemistry, 2005
- Transcriptional analysis of Ralstonia eutropha genes related to poly-(R)-3-hydroxybutyrate homeostasis during batch fermentationApplied Microbiology and Biotechnology, 2005
- The complex structure of polyhydroxybutyrate (PHB) granules: four orthologous and paralogous phasins occur in Ralstonia eutrophaMicrobiology, 2004
- Polyhydroxyalkanoate (PHA) homeostasis: the role of the PHA synthaseNatural Product Reports, 2003
- Ralstonia eutrophaH16 Encodes Two and Possibly Three Intracellular Poly[d-(−)-3-Hydroxybutyrate] Depolymerase GenesJournal of Bacteriology, 2003
- A Broad Host Range Mobilization System for In Vivo Genetic Engineering: Transposon Mutagenesis in Gram Negative BacteriaBio/Technology, 1983