title: The potato carotenoid cleavage dioxygenase 4 catalyzes a single cleavage of β-ionone ring-containing carotenes and non-epoxidated xanthophylls.
abstract: Down-regulation of the potato carotenoid cleavage dioxygenase 4 (StCCD4) transcript level led to tubers with altered morphology and sprouting activity, which also accumulated higher levels of violaxanthin and lutein leading to elevated carotenoid amounts. This phenotype indicates a role of this enzyme in tuber development, which may be exerted by a cleavage product. In this work, we investigated the enzymatic activity of StCCD4, by expressing the corresponding cDNA in carotenoid accumulating Escherichia coli strains and by performing in vitro assays with heterologously expressed enzyme. StCCD4 catalyzed the cleavage of all-trans-β-carotene at the C9'-C10' double bond, leading to β-ionone and all-trans-β-apo-10'-carotenal, both in vivo and in vitro. The enzyme also cleaved β,β-cryptoxanthin, zeaxanthin and lutein either at the C9'-C10' or the C9-C10 double bond in vitro. In contrast, we did not observe any conversion of violaxanthin and only traces of activity with 9-cis-β-carotene, which led to 9-cis-β-apo-10'-carotenal. Our data indicate that all-trans-β-carotene is the likely substrate of StCCD4 in planta, and that this carotene may be precursor of an unknown compound involved in tuber development.
authors.affiliation: Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
authors.forename: Mark
authors.initials: M
authors.lastname: Bruno
authors.affiliation: Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Beyer
authors.affiliation: Center for Desert Agriculture, BESE Division, King Abdullah University of Science and Technology (KAUST), 23955-6900 Thuwal, Saudi Arabia; Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany. Electronic address: salim.babili@kaust.edu.sa.
authors.forename: Salim
authors.initials: S
authors.lastname: Al-Babili
mesh_terms: D055162:Biocatalysis; D049308:Dioxygenases / Q000378:metabolism*; D045792:Norisoprenoids / Q000737:chemistry*; D011198:Solanum tuberosum / Q000201:enzymology*; D024341:Xanthophylls / Q000737:chemistry / Q000378:metabolism*; D019207:beta Carotene / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D045792:Norisoprenoids; D024341:Xanthophylls; D019207:beta Carotene; C008157:beta-ionone; D049308:Dioxygenases
keywords: Apocarotenoids; Carotenoid cleavage dioxygenases; Carotenoids; Potato