Influence of L-fucose attached alpha 1-->6 to the asparagine-linked N-acetylglucosamine on the hydrolysis of the N-glycosidic linkage by human glycosylasparaginase.
The sequence of hydrolytic reactions in the catabolism of the N-glycosidic oligosaccharide-to-protein region containing 6-linked fucose on the asparagine-linked N-acetylglucosamine may vary from species to species. When alpha-L-fucopyranosyl-(1-->6)-2-acetamido-1-N-(beta-L-aspartyl)-2-deoxy- beta -D-glucopyranosylamine (Fuc-GlcNAc-Asn) was incubated with recombinant human glycosylasparaginase, no hydrolysis of the N-glycosidic bond was detected. After removal of the alpha 1-->6-linked fucose from the compound by alpha-fucosidase, the residual GlcNAc-Asn was rapidly hydrolyzed by glycosylasparaginase. Enzymologically this demonstrates for the first time that the catabolism of Fuc-GlcNAc-Asn in humans occurs via consecutive action of alpha-fucosidase and glycosylasparaginase. The hydrolysis rate of GlcNAc-Asn by glycosylasparaginase remained unaffected in the presence of Fuc-GlcNAc-Asn or several different monosaccharides including fucose. This indicates that any fucose attached alpha 1-->6 to the asparagine-linked N-acetylglucosamine residue prevents the access of the L-asparagine residue of Fuc-GlcNAc-Asn into the deep, funnel-shaped active site of human glycosylasparaginase. These findings explain the accumulation of fucosylated and normal catabolism of nonfucosylated glycoasparagines in fucosidosis.
Noronkoski
T
T
Department of Clinical Chemistry, Kuopio University Hospital, Finland.
Mononen
I
I
D000117:Acetylglucosamine / Q000378:metabolism; D001227:Aspartylglucosylaminase / Q000235:genetics / Q000378:metabolism*; D005643:Fucose / Q000378:metabolism; D005645:Fucosidosis / Q000209:etiology; D006027:Glycosides / Q000378:metabolism*; D006801:Humans; D011994:Recombinant Proteins / Q000378:metabolism; D013045:Species Specificity; D013379:Substrate Specificity; D005644:alpha-L-Fucosidase / Q000378:metabolism
D006027:Glycosides; D011994:Recombinant Proteins; D005643:Fucose; D005644:alpha-L-Fucosidase; D001227:Aspartylglucosylaminase; D000117:Acetylglucosamine