title: Enoyl-CoA hydratase mediates polyhydroxyalkanoate mobilization in Haloferax mediterranei.
abstract: Although polyhydroxyalkanoate (PHA) accumulation and mobilization are one of the most general mechanisms for haloarchaea to adapt to the hypersaline environments with changeable carbon sources, the PHA mobilization pathways are still not clear for any haloarchaea. In this study, the functions of five putative (R)-specific enoyl-CoA hydratases (R-ECHs) in Haloferax mediterranei, named PhaJ1 to PhaJ5, respectively, were thoroughly investigated. Through gene deletion and complementation, we demonstrated that only certain of these ECHs had a slight contribution to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biosynthesis. But significantly, PhaJ1, the only R-ECH that is associated with PHA granules, was shown to be involved in PHA mobilization in this haloarchaeon. PhaJ1 catalyzes the dehydration of (R)-3-hydroxyacyl-CoA, the common product of PHA degradation, to enoyl-CoA, the intermediate of the β-oxidation cycle, thus could link PHA mobilization to β-oxidation pathway in H. mediterranei. This linkage was further indicated from the up-regulation of the key genes of β-oxidation under the PHA mobilization condition, as well as the obvious inhibition of PHA degradation upon inhibition of the β-oxidation pathway. Interestingly, 96% of phaJ-containing haloarchaeal species possess both phaC (encoding PHA synthase) and the full set genes of β-oxidation, implying that the mobilization of carbon storage in PHA through the β-oxidation cycle would be general in haloarchaea.
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.|CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Guiming
authors.initials: G
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Shuangfeng
authors.initials: S
authors.lastname: Cai
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Hou
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Dahe
authors.initials: D
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Han
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Xiang
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004746:Enoyl-CoA Hydratase / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D019848:Gene Expression Regulation, Archaeal; D015971:Gene Expression Regulation, Enzymologic; D019623:Haloferax mediterranei / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D010421:Pentanoic Acids / Q000378:metabolism; D010802:Phylogeny; D054813:Polyhydroxyalkanoates / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D000214:Acyl Coenzyme A; D019843:Archaeal Proteins; D007527:Isoenzymes; D010421:Pentanoic Acids; D054813:Polyhydroxyalkanoates; C010701:crotonyl-coenzyme A; D004746:Enoyl-CoA Hydratase; C038780:n-pentanoic acid