title: Use of in vivo 13C nuclear magnetic resonance spectroscopy to elucidate L-arabinose metabolism in yeasts.
abstract: Candida arabinofermentans PYCC 5603(T) and Pichia guilliermondii PYCC 3012 were shown to grow well on L-arabinose, albeit exhibiting distinct features that justify an in-depth comparative study of their respective pentose catabolism. Carbon-13 labeling experiments coupled with in vivo nuclear magnetic resonance (NMR) spectroscopy were used to investigate L-arabinose metabolism in these yeasts, thereby complementing recently reported physiological and enzymatic data. The label supplied in L-[2-(13)C]arabinose to nongrowing cells, under aerobic conditions, was found on C-1 and C-2 of arabitol and ribitol, on C-2 of xylitol, and on C-1, C-2, and C-3 of trehalose. The detection of labeled arabitol and xylitol constitutes additional evidence for the operation in yeast of the redox catabolic pathway, which is widespread among filamentous fungi. Furthermore, labeling at position C-1 of trehalose and arabitol demonstrates that glucose-6-phosphate is recycled through the oxidative pentose phosphate pathway (PPP). This result was interpreted as a metabolic strategy to regenerate NADPH, the cofactor essential for sustaining l-arabinose catabolism at the level of L-arabinose reductase and L-xylulose reductase. Moreover, the observed synthesis of D-arabitol and ribitol provides a route with which to supply NAD(+) under oxygen-limiting conditions. In P. guilliermondii PYCC 3012, the strong accumulation of L-arabitol (intracellular concentration of up to 0.4 M) during aerobic L-arabinose metabolism indicates the existence of a bottleneck at the level of L-arabitol 4-dehydrogenase. This report provides the first experimental evidence for a link between L-arabinose metabolism in fungi and the oxidative branch of the PPP and suggests rational guidelines for the design of strategies for the production of new and efficient L-arabinose-fermenting yeasts.
authors.affiliation: Centro de Recursos Microbiológicos, Department of Life Sciences, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: César
authors.initials: C
authors.lastname: Fonseca
authors.forename: Ana Rute
authors.initials: AR
authors.lastname: Neves
authors.forename: Alexandra M M
authors.initials: AM
authors.lastname: Antunes
authors.forename: João Paulo
authors.initials: JP
authors.lastname: Noronha
authors.forename: Bärbel
authors.initials: B
authors.lastname: Hahn-Hägerdal
authors.forename: Helena
authors.initials: H
authors.lastname: Santos
authors.forename: Isabel
authors.initials: I
authors.lastname: Spencer-Martins
mesh_terms: D001089:Arabinose / Q000737:chemistry / Q000378:metabolism*; D002247:Carbon Isotopes / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008954:Models, Biological; D012255:Ribitol / Q000737:chemistry / Q000378:metabolism; D013402:Sugar Alcohols / Q000737:chemistry / Q000378:metabolism; D014199:Trehalose / Q000737:chemistry / Q000378:metabolism; D014993:Xylitol / Q000737:chemistry / Q000378:metabolism; D015003:Yeasts / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D013402:Sugar Alcohols; D012255:Ribitol; D001089:Arabinose; D014199:Trehalose; D014993:Xylitol; C014999:arabitol