RESUMO
The article "Metabolism of L-arabinose in plants", written by "Toshihisa Kotake, Yukiko Yamanashi, Chiemi Imaizumi, Yoichi Tsumuraya", was originally published Online First without open access. After publication in volume129, issue 5, page 781-792 the Botanical Society of Japan decided to opt for Open Choice and to make the article an open access publication.
RESUMO
The major plant sugar l-arabinose (l-Ara) has two different ring forms, l-arabinofuranose (l-Araf) and l-arabinopyranose (l-Arap). Although l-Ara mainly appears in the form of α-l-Araf residues in cell wall components, such as pectic α-1,3:1,5-arabinan, arabinoxylan, and arabinogalactan-proteins (AGPs), lesser amounts of it can also be found as ß-l-Arap residues of AGPs. Even though AGPs are known to be rapidly metabolized, the enzymes acting on the ß-l-Arap residues remain to be identified. In the present study, four enzymes, which we call ß-l-ARAPASE (APSE) and α-GALACTOSIDASE 1 (AGAL1), AGAL2, and AGAL3, are identified as those enzymes that are likely to be responsible for the hydrolysis of the ß-l-Arap residues in Arabidopsis thaliana. An Arabidopsis apse-1 mutant showed significant reduction in ß-l-arabinopyranosidase activity, and an apse-1 agal3-1 double-mutant exhibited even less activity. The apse-1 and the double-mutants both had more ß-l-Arap residues in the cell walls than wild-type plants. Recombinant APSE expressed in the yeast Pichia pastoris specifically hydrolyzed ß-l-Arap residues and released l-Ara from gum arabic and larch arabinogalactan. The recombinant AGAL3 also showed weak ß-l-arabinopyranosidase activity beside its strong α-galactosidase activity. It appears that the ß-l-Arap residues of AGPs are hydrolysed mainly by APSE and partially by AGALs in Arabidopsis.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , alfa-Galactosidase/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Arabinose/análogos & derivados , Arabinose/metabolismo , Parede Celular/genética , Parede Celular/metabolismo , Glicosídeo Hidrolases/genética , Glicosídeo Hidrolases/metabolismo , Hidrólise , Hipocótilo/genética , Hipocótilo/crescimento & desenvolvimento , Mutação , Filogenia , Pichia/genética , Plantas Geneticamente Modificadas , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Especificidade por Substrato , alfa-Galactosidase/genéticaRESUMO
L-Arabinose (L-Ara) is a plant-specific sugar accounting for 5-10 % of cell wall saccharides in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa). L-Ara occurs in pectic arabinan, rhamnogalacturonan II, arabinoxylan, arabinogalactan-protein (AGP), and extensin in the cell walls, as well as in glycosylated signaling peptides like CLAVATA3 and small glycoconjugates such as quercetin 3-O-arabinoside. This review focuses on recent advances towards understanding the generation of L-Ara and the metabolism of L-Ara-containing molecules in plants.