title: Characterisation and biosynthesis of D-erythroascorbic acid in Phycomyces blakesleeanus.
abstract: D-Erythroascorbate and D-erythroascorbate glucoside have been identified in the Zygomycete fungus Phycomyces blakesleeanus. Ascomycete and Basidiomycete fungi also synthesise D-erythroascorbate instead of l-ascorbate, suggesting that D-erythroascorbate synthesis evolved in the common ancestor of the fungi. Both compounds accumulate in P. blakesleeanus at higher levels than observed in other fungal species. D-Erythroascorbate glucoside reduced dichlorophenolindophenol as effectively as L-ascorbate, but was more stable to autoxidation. D-Erythroascorbate glucoside predominated in spores and stationary phase mycelium. Free D-erythroascorbate accumulated during the exponential phase of mycelial growth and decreased to very low levels in the stationary phase. This suggests an association between growth and free D-erythroascorbate. P. blakesleeanus converted exogenous D-arabinose to D-erythroascorbate and its glucoside. A monomeric NAD-dependent D-arabinose dehydrogenase of 41 kDa was purified to near homogeneity. The enzyme oxidised D-arabinose, L-galactose, and L-fucose. Correspondingly, mycelium converted exogenous L-galactose and L-fucose to L-ascorbate and 6-deoxyascorbate, respectively. The antioxidant role of D-erythroascorbate and its glucoside is discussed.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Universidad de León, León, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Baroja-Mazo
authors.forename: Pilar
authors.initials: P
authors.lastname: del Valle
authors.forename: Javier
authors.initials: J
authors.lastname: Rúa
authors.forename: Sergio
authors.initials: S
authors.lastname: de Cima
authors.forename: Félix
authors.initials: F
authors.lastname: Busto
authors.forename: Dolores
authors.initials: D
authors.lastname: de Arriaga
authors.forename: Nicholas
authors.initials: N
authors.lastname: Smirnoff
mesh_terms: D015086:2,6-Dichloroindophenol / Q000737:chemistry; D001089:Arabinose / Q000378:metabolism; D001205:Ascorbic Acid / Q000096:biosynthesis* / Q000737:chemistry*; D005643:Fucose / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D006031:Glycosylation; D008970:Molecular Weight; D025282:Mycelium / Q000737:chemistry; D010084:Oxidation-Reduction; D010800:Phycomyces / Q000201:enzymology / Q000378:metabolism*; D013170:Spores / Q000737:chemistry; D013401:Sugar Alcohol Dehydrogenases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D005643:Fucose; C005056:isoascorbic acid; D001089:Arabinose; D015086:2,6-Dichloroindophenol; D013401:Sugar Alcohol Dehydrogenases; C028590:D-arabinose dehydrogenase; D001205:Ascorbic Acid; D005690:Galactose