Publications

• Isolation, characterization, and expression of cDNAs encoding murine alpha-mannosidase II, a Golgi enzyme that controls conversion of high mannose to complex N-glycans.

  Moremen K.W., Robbins P.W.

  Golgi alpha-mannosidase II (GlcNAc transferase I-dependent alpha 1,3[alpha 1,6] mannosidase, EC 3.2.1.114) catalyzes the final hydrolytic step in the N-glycan maturation pathway acting as the committed step in the conversion of high mannose to complex type structures. We have isolated overlapping ... >> More

  Golgi alpha-mannosidase II (GlcNAc transferase I-dependent alpha 1,3[alpha 1,6] mannosidase, EC 3.2.1.114) catalyzes the final hydrolytic step in the N-glycan maturation pathway acting as the committed step in the conversion of high mannose to complex type structures. We have isolated overlapping clones from a murine cDNA library encoding the full length alpha-mannosidase II open reading frame and most of the 5' and 3' untranslated region. The coding sequence predicts a type II transmembrane protein with a short cytoplasmic tail (five amino acids), a single transmembrane domain (21 amino acids), and a large COOH-terminal catalytic domain (1,124 amino acids). This domain organization which is shared with the Golgi glycosyl-transferases suggests that the common structural motifs may have a functional role in Golgi enzyme function or localization. Three sets of polyadenylated clones were isolated extending 3' beyond the open reading frame by as much as 2,543 bp. Northern blots suggest that these polyadenylated clones totaling 6.1 kb in length correspond to minor message species smaller than the full length message. The largest and predominant message on Northern blots (7.5 kb) presumably extends another approximately 1.4-kb downstream beyond the longest of the isolated clones. Transient expression of the alpha-mannosidase II cDNA in COS cells resulted in 8-12-fold overexpression of enzyme activity, and the appearance of cross-reactive material in a perinuclear membrane array consistent with a Golgi localization. A region within the catalytic domain of the alpha-mannosidase II open reading frame bears a strong similarity to a corresponding sequence in the rat liver endoplasmic reticulum alpha-mannosidase and the vacuolar alpha-mannosidase of Saccharomyces cerevisiae. Partial human alpha-mannosidase II cDNA clones were also isolated and the gene was localized to human chromosome 5. << Less

  J. Cell Biol. 115:1521-1534(1991) [PubMed] [EuropePMC]

• Golgi alpha-mannosidase II cleaves two sugars sequentially in the same catalytic site.

  Shah N., Kuntz D.A., Rose D.R.

  Golgi alpha-mannosidase II (GMII) is a key glycosyl hydrolase in the N-linked glycosylation pathway. It catalyzes the removal of two different mannosyl linkages of GlcNAcMan(5)GlcNAc(2), which is the committed step in complex N-glycan synthesis. Inhibition of this enzyme has shown promise in certa ... >> More

  Golgi alpha-mannosidase II (GMII) is a key glycosyl hydrolase in the N-linked glycosylation pathway. It catalyzes the removal of two different mannosyl linkages of GlcNAcMan(5)GlcNAc(2), which is the committed step in complex N-glycan synthesis. Inhibition of this enzyme has shown promise in certain cancers in both laboratory and clinical settings. Here we present the high-resolution crystal structure of a nucleophile mutant of Drosophila melanogaster GMII (dGMII) bound to its natural oligosaccharide substrate and an oligosaccharide precursor as well as the structure of the unliganded mutant. These structures allow us to identify three sugar-binding subsites within the larger active site cleft. Our results allow for the formulation of the complete catalytic process of dGMII, which involves a specific order of bond cleavage, and a major substrate rearrangement in the active site. This process is likely conserved for all GMII enzymes-but not in the structurally related lysosomal mannosidase-and will form the basis for the design of specific inhibitors against GMII. << Less

  Proc Natl Acad Sci U S A 105:9570-9575(2008) [PubMed] [EuropePMC]

• The synthesis of complex-type oligosaccharides. III. Identification of an alpha-D-mannosidase activity involved in a late stage of processing of complex-type oligosaccharides.

  Tabas I., Kornfeld S.

  J Biol Chem 253:7779-7786(1978) [PubMed] [EuropePMC]

• Structure, mechanism and inhibition of Golgi alpha-mannosidase II.

  Rose D.R.

  The mature N-glycan on human glycoproteins is built up by the activity and regulation of enzymes in the endoplasmic reticulum and Golgi apparatus. A key enzyme in the maturation of N-glycans is the first glycoside hydrolase in the Golgi pathway, α-mannosidase II (GMII). This enzyme has the unusual ... >> More

  The mature N-glycan on human glycoproteins is built up by the activity and regulation of enzymes in the endoplasmic reticulum and Golgi apparatus. A key enzyme in the maturation of N-glycans is the first glycoside hydrolase in the Golgi pathway, α-mannosidase II (GMII). This enzyme has the unusual ability to cleave two different glycosidic linkages in it catalytic center. As such, it removes two terminal mannoses following the activity of N-acetyl-glucosaminyl transferase I, and is a critical step in the formation of mature glycans. Structural analyses of the Drosophila homologue of GMII have led to insights into its unusual mechanism and substrate specificity. In addition, the results build the foundation for the development of specific clinically relevant inhibitors. << Less

  Curr Opin Struct Biol 22:558-562(2012) [PubMed] [EuropePMC]

• The production, purification and characterisation of two novel alpha-D-mannosidases from Aspergillus phoenicis.

  Athanasopoulos V.I., Niranjan K., Rastall R.A.

  1,6-alpha-D-Mannosidase from Aspergillus phoenicis was purified by anion-exchange chromatography, chromatofocussing and size-exclusion chromatography. The apparent molecular weight was 74 kDa by SDS-PAGE and 81 kDa by native-PAGE. The isoelectric point was 4.6. 1,6-alpha-D-Mannosidase had a temper ... >> More

  1,6-alpha-D-Mannosidase from Aspergillus phoenicis was purified by anion-exchange chromatography, chromatofocussing and size-exclusion chromatography. The apparent molecular weight was 74 kDa by SDS-PAGE and 81 kDa by native-PAGE. The isoelectric point was 4.6. 1,6-alpha-D-Mannosidase had a temperature optimum of 60 degrees C, a pH optimum of 4.0-4.5, a K(m) of 14 mM with alpha-D-Manp-(1-->6)-D-Manp as substrate. It was strongly inhibited by Mn(2+) and did not need Ca(2+) or any other metal cofactor of those tested. The enzyme cleaves specifically (1-->6)-linked mannobiose and has no activity towards any other linkages, p-nitrophenyl-alpha-D-mannopyranoside or baker's yeast mannan. 1,3(1,6)-alpha-D-Mannosidase from A. phoenicis was purified by anion-exchange chromatography, chromatofocussing and size-exclusion chromatography. The apparent molecular weight was 97 kDa by SDS-PAGE and 110 kDa by native-PAGE. The 1,3(1,6)-alpha-D-mannosidase enzyme existed as two charge isomers or isoforms. The isoelectric points of these were 4.3 and 4.8 by isoelectric focussing. It cleaves alpha-D-Manp-(1-->3)-D-Manp 10 times faster than alpha-D-Manp-(1-->6)-D-Manp, has very low activity towards p-nitrophenyl-alpha-D-mannopyranoside and baker's yeast mannan, and no activity towards alpha-D-Manp-(1-->2)-D-Manp. The activity towards (1-->3)-linked mannobiose is strongly activated by 1mM Ca(2+) and inhibited by 10mM EDTA, while (1-->6)-activity is unaffected, indicating that the two activities may be associated with different polypeptides. It is also possible that one polypeptide may have two active sites catalysing distinct activities. << Less

  Carbohydr Res 340:609-617(2005) [PubMed] [EuropePMC]

• Control of glycoprotein synthesis. Processing of asparagine-linked oligosaccharides by one or more rat liver Golgi alpha-D-mannosidases dependent on the prior action of UDP-N-acetylglucosamine: alpha-D-mannoside beta 2-N-acetylglucosaminyltransferase I.

  Harpaz N., Schachter H.

  J Biol Chem 255:4894-4902(1980) [PubMed] [EuropePMC]

• Purification and characterization of alpha-D-mannosidase from rat liver golgi membranes.

  Tulsiani D.R., Opheim D.J., Touster O.

  J Biol Chem 252:3227-3233(1977) [PubMed] [EuropePMC]

• alpha-D-Mannosidases of rat liver Golgi membranes. Mannosidase II is the GlcNAcMAN5-cleaving enzyme in glycoprotein biosynthesis and mannosidases Ia and IB are the enzymes converting Man9 precursors to Man5 intermediates.

  Tulsiani D.R., Hubbard S.C., Robbins P.W., Touster O.

  Current evidence indicates that the trimming of mannosyl residues from intermediates in the biosynthesis of the N-linked oligosaccharides of glycoproteins occurs in the Golgi complex. We now present evidence that mannosidase II (Tulsiani, D. R. P., Opheim, D. J., and Touster, O. (1977) J. Biol Che ... >> More

  Current evidence indicates that the trimming of mannosyl residues from intermediates in the biosynthesis of the N-linked oligosaccharides of glycoproteins occurs in the Golgi complex. We now present evidence that mannosidase II (Tulsiani, D. R. P., Opheim, D. J., and Touster, O. (1977) J. Biol Chem. 252, 3227-3233) is the Golgi enzyme that converts GlcNAc Man5 species to GlcNAcMan3 species in completing the mannosyl trimming process required in the biosynthesis of complex type glycoproteins. GlcNAc([3H]Man)5GlcNAc-mannosidase and p-nitrophenyl alpha-D-mannosidase activities copurify throughout the preparative procedure and show the same properties. In addition to mannosidase IA (Tabas, I., and Kornfeld, S. (1979) J. Biol. Chem. 254, 11655-11663), a second alpha-1,2-mannosidase (mannosidase IB) can be prepared from Golgi membranes which is effective in converting Man9GlcNAc to Man5GlcNAc. The two alpha-1,2-mannosidases are very similar in catalytic properties, but they are also distinguishable by several criteria. Although these two enzymes have not been extensively purified, several lines of evidence lead to the tentative conclusion that they are distinct enzymes. They appear to be present in comparable activities in the Golgi membranes and together account for the alpha-1,2-mannosidase activity of these membranes. The particular role of each alpha-1,2-mannosidase remains to be determined. << Less

  J Biol Chem 257:3660-3668(1982) [PubMed] [EuropePMC]

  This publication is cited by 9 other entries.

• Molecular cloning and expression of cDNAs encoding human alpha-mannosidase II and a previously unrecognized alpha-mannosidase IIx isozyme.

  Misago M., Liao Y.-F., Kudo S., Eto S., Mattei M.-G., Moremen K.W., Fukuda M.N.

  Golgi alpha-mannosidase II (alpha-MII) is an enzyme involved in the processing of N-linked glycans. Using a previously isolated murine cDNA clone as a probe, we have isolated cDNA clones encompassing the human alpha-MII cDNA open reading frame and initiated isolation of human genomic clones. Durin ... >> More

  Golgi alpha-mannosidase II (alpha-MII) is an enzyme involved in the processing of N-linked glycans. Using a previously isolated murine cDNA clone as a probe, we have isolated cDNA clones encompassing the human alpha-MII cDNA open reading frame and initiated isolation of human genomic clones. During the isolation of genomic clones, genes related to that encoding alpha-MII were isolated. One such gene was found to encode an isozyme, designated alpha-MIIx. A 5-kb cDNA clone encoding alpha-MIIx was then isolated from a human melanoma cDNA library. However, comparison between alpha-MIIx and alpha-MII cDNAs suggested that the cloned cDNA encodes a truncated polypeptide with 796 amino acid residues, while alpha-MII consists of 1144 amino acid residues. To reevaluate the sequence of alpha-MIIx cDNA, polymerase chain reaction (PCR) was performed with lymphocyte mRNAs. Comparison of the sequence of PCR products with the alpha-MIIx genomic sequence revealed that alternative splicing of the alpha-MIIx transcript can result in an additional transcript encoding a 1139-amino acid polypeptide. Northern analysis showed transcription of alpha-MIIx in various tissues, suggesting that the alpha-MIIx gene is a housekeeping gene. COS cells transfected with alpha-MIIx cDNA containing the full-length open reading frame showed an increase of alpha-mannosidase activity. The alpha-MIIx gene was mapped to human chromosome 15q25, whereas the alpha-MII gene was mapped to 5q21-22. << Less

  Proc. Natl. Acad. Sci. U.S.A. 92:11766-11770(1995) [PubMed] [EuropePMC]

• Structure of Golgi alpha-mannosidase II: a target for inhibition of growth and metastasis of cancer cells.

  van den Elsen J.M., Kuntz D.A., Rose D.R.

  Golgi alpha-mannosidase II, a key enzyme in N-glycan processing, is a target in the development of anti-cancer therapies. The crystal structure of Drosophila Golgi alpha-mannosidase II in the absence and presence of the anti-cancer agent swainsonine and the inhibitor deoxymannojirimycin reveals a ... >> More

  Golgi alpha-mannosidase II, a key enzyme in N-glycan processing, is a target in the development of anti-cancer therapies. The crystal structure of Drosophila Golgi alpha-mannosidase II in the absence and presence of the anti-cancer agent swainsonine and the inhibitor deoxymannojirimycin reveals a novel protein fold with an active site zinc intricately involved both in the substrate specificity of the enzyme and directly in the catalytic mechanism. Identification of a putative GlcNAc binding pocket in the vicinity of the active site cavity provides a model for the binding of the GlcNAcMan(5)GlcNAc(2) substrate and the consecutive hydrolysis of the alpha1,6- and alpha1,3-linked mannose residues. The enzyme-inhibitor interactions observed provide insight into the catalytic mechanism, opening the door to the design of novel inhibitors of alpha-mannosidase II. << Less

  EMBO J 20:3008-3017(2001) [PubMed] [EuropePMC]