[Comparative study of lysosomal and cytosolic catabolisms of oligomannosidic-type glycans].
In order to study the substrate specificities of the enzymes implicated in the catabolism of oligomannosidic-type glycans, the oligosaccharides Man9GlcNAc and Man5GlcNAc were incubated with rat liver lysosomal and cytosolic alpha-D-mannosidases and the hydrolysis products were characterized by 400 MHz 1H-NMR spectroscopy. Although they both occur in an ordered way, the two catabolic pathways are quite different. The lysomal pathway is realized in two stages: the first leads from Man9GlcNAc to Man5GlcNAc by preferential cleavage of the four alpha-1,2-linked mannose residues, and the second, Zn(2+)-dependent, leads from Man5GlcNAc to Man (beta 1-4) GlcN Ac by hydrolysis of alpha-1, 3- and alpha-1,6-linked residues. On the contrary, the cytosolic pattern leads by a pathway quite different to a unique hexasaccharide Man5GlcNAc which has, curiously, the same structure as one of the polyprenolic intermediates occurring in the cytosol during the biosynthesis of N-glycosylprotein glycans: Man (alpha 1-2) Man (alpha 1-2) Man (alpha 1-3) [Man (alpha 1-6)] Man (beta 1-4) GlcN Ac (beta 1-4) GlcNAc alpha 1-P-P-Dol.
Haeuw
J F
JF
Laboratoire de Chimie biologique, Université des Sciences et Techniques de Lille-Flandres-Artois, Villeneuve-d' Ascq.
Strecker
G
G
Wieruszeski
J M
JM
Montreuil
J
J
Michalski
J C
JC
D000818:Animals; D003600:Cytosol / Q000201:enzymology*; D008099:Liver / Q000648:ultrastructure; D008247:Lysosomes / Q000201:enzymology*; D009682:Magnetic Resonance Spectroscopy; D008361:Mannosidases / Q000378:metabolism*; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D051381:Rats
D009844:Oligosaccharides; D008361:Mannosidases
Etude comparée des catabolismes lysosomique et cytosolique des glycannes de type oligommannosidique.