Processing glycosidases of Saccharomyces cerevisiae.
The properties of the N-glycan processing glycosidases located in the endoplasmic reticulum of Saccharomyces cerevisiae are described. alpha-Glucosidase I encoded by CWH41 cleaves the terminal alpha1, 2-linked glucose and alpha-glucosidase II encoded by ROT2 removes the two alpha1,3-linked glucose residues from the Glc3Man9GlcNAc2 oligosaccharide precursor while the alpha1,2-mannosidase encoded by MNS1 removes one specific mannose to form a single isomer of Man8GlcNAc2. Although trimming by these glycosidases is not essential for the formation of N-glycan outer chains, recent studies on mutants lacking these enzymes indicate that alpha-glucosidases I and II play an indirect role in cell wall beta1,6-glucan formation and that the alpha1,2-mannosidase is involved in endoplasmic reticulum quality control. Detailed structure-function studies of recombinant yeast alpha1,2-mannosidase are described that serve as a model for other members of this enzyme family that has been conserved through eukaryotic evolution.
Herscovics
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McGill Cancer Centre, McGill University, 3655 Drummond Street, Montreal, Que. H3G 1Y6, Canada. annette@med.mcgill.ca
D004721:Endoplasmic Reticulum / Q000201:enzymology; D008361:Mannosidases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011134:Polysaccharides / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D013329:Structure-Activity Relationship; D000520:alpha-Glucosidases / Q000378:metabolism*; D001617:beta-Glucosidase / Q000378:metabolism*
D011134:Polysaccharides; D008361:Mannosidases; C046090:mannosyl-oligosaccharide 1,2-alpha-mannosidase; D000520:alpha-Glucosidases; D001617:beta-Glucosidase