title: Molecular and biochemical characterization of mannitol-1-phosphate dehydrogenase from the model brown alga Ectocarpus sp.
abstract: The sugar alcohol mannitol is important in the food, pharmaceutical, medical and chemical industries. It is one of the most commonly occurring polyols in nature, with the exception of Archaea and animals. It has a range of physiological roles, including as carbon storage, compatible solute, and osmolyte. Mannitol is present in large amounts in brown algae, where its synthesis involved two steps: a mannitol-1-phosphate dehydrogenase (M1PDH) catalyzes a reversible reaction between fructose-6-phosphate (F6P) and mannitol-1-phosphate (M1P) (EC 1.1.1.17), and a mannitol-1-phosphatase hydrolyzes M1P to mannitol (EC 3.1.3.22). Analysis of the model brown alga Ectocarpus sp. genome provided three candidate genes for M1PDH activities. We report here the sequence analysis of Ectocarpus M1PDHs (EsM1PDHs), and the biochemical characterization of the recombinant catalytic domain of EsM1PDH1 (EsM1PDH1cat). Ectocarpus M1PDHs are representatives of a new type of modular M1PDHs among the polyol-specific long-chain dehydrogenases/reductases (PSLDRs). The N-terminal domain of EsM1PDH1 was not necessary for enzymatic activity. Determination of kinetic parameters indicated that EsM1PDH1cat displayed higher catalytic efficiency for F6P reduction compared to M1P oxidation. Both activities were influenced by NaCl concentration and inhibited by the thioreactive compound pHMB. These observations were completed by measurement of endogenous M1PDH activity and of EsM1PDH gene expression during one diurnal cycle. No significant changes in enzyme activity were monitored between day and night, although transcription of two out of three genes was altered, suggesting different levels of regulation for this key metabolic pathway in brown algal physiology.
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff cedex, France. Electronic address: patricia.bonin@outlook.com.
authors.forename: Patricia
authors.initials: P
authors.lastname: Bonin
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff cedex, France. Electronic address: groisill@sb-roscoff.fr.
authors.forename: Agnès
authors.initials: A
authors.lastname: Groisillier
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff cedex, France. Electronic address: alice.raimbault@orange.fr.
authors.forename: Alice
authors.initials: A
authors.lastname: Raimbault
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff cedex, France. Electronic address: anais.guibert02@gmail.com.
authors.forename: Anaïs
authors.initials: A
authors.lastname: Guibert
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff cedex, France. Electronic address: boyen@sb-roscoff.fr.
authors.forename: Catherine
authors.initials: C
authors.lastname: Boyen
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff cedex, France. Electronic address: tonon@sb-roscoff.fr.
authors.forename: Thierry
authors.initials: T
authors.lastname: Tonon
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D007700:Kinetics; D008969:Molecular Sequence Data; D000459:Phaeophyceae / Q000201:enzymology* / Q000235:genetics; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D020539:Sequence Analysis, Protein; D013401:Sugar Alcohol Dehydrogenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D013401:Sugar Alcohol Dehydrogenases; C021544:mannitol-1-phosphate dehydrogenase
keywords: Brown algae; Ectocarpus sp.; Mannitol cycle; Mannitol-1-phosphate dehydrogenase; Recombinant protein