Molecular and biochemical characterization of mannitol-1-phosphate dehydrogenase from the model brown alga Ectocarpus sp. (September 2015)

• Record Type: Journal Article
• Authors: Bonin, Patricia; Groisillier, Agnès; Raimbault, Alice; Guibert, Anaïs; Boyen, Catherine; Tonon, Thierry
• Is Part Of: Phytochemistry. Volume 117(2015:Sep.)
• Page Start: 509
• Page End: 520
• Publication Date: 2015-09
• Subjects: Brown algae -- Ectocarpus sp. -- Mannitol cycle -- Mannitol-1-phosphate dehydrogenase -- Recombinant protein; Botanical chemistry -- Periodicals; Biochemistry -- Periodicals; Botany -- Periodicals; Chimie végétale -- Périodiques; 572.2
• DOI: 10.1016/j.phytochem.2015.07.015
• Languages: English
• ISSNs: 0031-9422

Abstract

Graphical abstract: Mannitol metabolism plays key roles in the physiology of brown algae. This article describes the biochemical characterization of the recombinant catalytic domain of one mannitol-1-phosphate dehydrogenase (M1PDH) of the model organism Ectocarpus sp. Highlights: Brown algal mannitol-1-phosphate dehydrogenases (M1PDHs) are modular proteins. These enzymes represent a distinct type of M1PDHs compared to microbial sequences. Recombinant catalytic domain of Ectocarpus M1PDH1 was biochemically characterized. The N-terminal domain of EsM1PDH1 is not necessary for catalytic activity. 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.