title: cpFBPaseII, a novel redox-independent chloroplastic isoform of fructose-1,6-bisphosphatase.
abstract: A full-length FBPase cDNA has been isolated from Fragaria x ananassa (strawberry) corresponding to a novel putative chloroplastic FBPase but lacking the regulatory redox domain, a characteristic of the plastidial isoenzyme (cpFBPaseI). Another outstanding feature of this novel isoform, called cpFBPaseII, is the absence of the canonical active site. Enzymatic assays with cpFBPaseII evidenced clear Mg(2+)-dependent FBPase activity and a K(m) for fructose-1,6-bisphosphate (FBP) of 1.3 mM. Immunolocalization experiments and chloroplast isolation confirmed that the new isoenzyme is located in the stroma. Nevertheless, unlike cpFBPaseI, which is redox activated, cpFBPaseII did not increase its activity in the presence of either DTT or thioredoxin f (TRX f) and is resistant to H(2)O(2) inactivation. Additionally, the novel isoform was able to complement the growth deficiency of the yeast FBP1 deletion fed with a non-fermentable carbon source. Furthermore, orthologues are restricted to land plants, suggesting that cpFBPaseII is a novel and an intriguing chloroplastic FBPase that emerged late in the evolution of photosynthetic organisms, possibly because of a pressing need of land plants.
authors.affiliation: Estación Experimental del Zaidín (CSIC), Profesor Albareda, 1, 18008-Granada, Spain.
authors.forename: Antonio Jesús
authors.initials: AJ
authors.lastname: Serrato
authors.forename: Elena María
authors.initials: EM
authors.lastname: Yubero-Serrano
authors.forename: Luisa María
authors.initials: LM
authors.lastname: Sandalio
authors.forename: Juan
authors.initials: J
authors.lastname: Muñoz-Blanco
authors.forename: Ana
authors.initials: A
authors.lastname: Chueca
authors.forename: José Luis
authors.initials: JL
authors.lastname: Caballero
authors.forename: Mariam
authors.initials: M
authors.lastname: Sahrawy
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D002736:Chloroplasts / Q000201:enzymology*; D019295:Computational Biology; D018076:DNA, Complementary; D018744:DNA, Plant / Q000235:genetics; D031985:Fragaria / Q000201:enzymology* / Q000235:genetics; D006597:Fructose-Bisphosphatase / Q000235:genetics / Q000378:metabolism*; D017343:Genes, Plant; D005816:Genetic Complementation Test; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D007527:Isoenzymes; D006597:Fructose-Bisphosphatase