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Gewählte Publikation:

Strasser, R; Bondili, JS; Schoberer, J; Svoboda, B; Liebminger, E; Glössl, J; Altmann, F; Steinkellner, H; Mach, L; .
(2007): Enzymatic properties and subcellular localization of Arabidopsis beta-N-acetylhexosaminidases.
Plant Physiol. 2007; 145(1):5-16 FullText FullText_BOKU

Plant glycoproteins contain substantial amounts of paucimannosidic N- glycans lacking terminal GlcNAc residues at their nonreducing ends. It has been proposed that this is due to the action of beta-hexosaminidases during late stages of N-glycan processing or in the course of N-glycan turnover. We have now cloned the three putative beta-hexosaminidase sequences present in the Arabidopsis (Arabidopsis thaliana) genome. When heterologously expressed as soluble forms in Spodoptera frugiperda cells, the enzymes (termed HEXO1-3) could all hydrolyze the synthetic substrates p-nitrophenyl-2-acetamido-2-deoxy-beta-D-glucopyranoside, p-nitrophenyl-2-acetamido-2-deoxy-beta-D-galactopyranoside, 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-Dglucopyranoside, and 4-methylumbelliferyl-6-sulfo-2-acetamido-2-deoxy-beta-D-glucopyranoside, albeit to a varying extent. HEXO1 to HEXO3 were further able to degrade pyridylaminated chitotriose, whereas pyridylaminated chitobiose was only cleaved by HEXO1. With N-glycan substrates, HEXO1 displayed a much higher specific activity than HEXO2 and HEXO3. Nevertheless, all three enzymes were capable of removing terminal GlcNAc residues from the alpha 1,3-and alpha 1,6-mannosyl branches of biantennary N-glycans without any strict branch preference. Subcellular localization studies with HEXO-fluorescent protein fusions transiently expressed in Nicotiana benthamiana plants showed that HEXO1 is a vacuolar protein. In contrast, HEXO2 and HEXO3 are mainly located at the plasma membrane. These results indicate that HEXO1 participates in N-glycan trimming in the vacuole, whereas HEXO2 and/or HEXO3 could be responsible for the processing of N-glycans present on secretory glycoproteins.
Autor*innen der BOKU Wien:
Altmann Friedrich
Glößl Josef
Mach Lukas
Schoberer Jennifer
Steinkellner Herta
Strasser Richard
Find related publications in this database (using NML MeSH Indexing)
Amino Acid Sequence;Animals;Arabidopsis/enzymology*;Arabidopsis/genetics;Cloning, Molecular;DNA, Complementary;Gene Expression;Humans;Molecular Sequence Data;Proteoglycans/metabolism*;Recombinant Proteins/metabolism;Spodoptera/genetics;Spodoptera/metabolism*;beta-N-Acetylhexosaminidases/genetics;beta-N-Acetylhexosaminidases/metabolism*;

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