The Enzyme Database

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EC 2.4.1.101     
Accepted name: α-1,3-mannosyl-glycoprotein 2-β-N-acetylglucosaminyltransferase
Reaction: UDP-N-acetyl-α-D-glucosamine + Man5GlcNAc2-[protein] = UDP + Man5GlcNAc3-[protein]
For diagram of mannosyl-glycoprotein N-acetylglucosaminyltransferases, click here
Glossary: Man5GlcNAc2-[protein] = α-D-Man-(1→3)-[α-D-Man-(1→3)-[α-D-Man-(1→6)]-α-D-Man-(1→6)]-β-D-Man-(1→4)-β-D-GlcNAc-(1→4)-α-D-GlcNAc-N-Asn-[protein]
Man5GlcNAc3-[protein]= β-D-GlcNAc-(1→2)-α-D-Man-(1→3)-[α-D-Man-(1→3)-[α-D-Man-(1→6)]-α-D-Man-(1→6)]-β-D-Man-(1→4)-β-D-GlcNAc-(1→4)-α-D-GlcNAc-N-Asn-[protein]
Other name(s): MGAT1 (gene name); N-acetylglucosaminyltransferase I; N-glycosyl-oligosaccharide-glycoprotein N-acetylglucosaminyltransferase I; uridine diphosphoacetylglucosamine-α-1,3-mannosylglycoprotein β-1,2-N-acetylglucosaminyltransferase; UDP-N-acetylglucosaminyl:α-1,3-D-mannoside-β-1,2-N-acetylglucosaminyltransferase I; UDP-N-acetylglucosaminyl:α-3-D-mannoside β-1,2-N-acetylglucosaminyltransferase I; α-1,3-mannosyl-glycoprotein β-1,2-N-acetylglucosaminyltransferase; GnTI; GlcNAc-T I; UDP-N-acetyl-D-glucosamine:3-(α-D-mannosyl)-β-D-mannosyl-glycoprotein 2-β-N-acetyl-D-glucosaminyltransferase
Systematic name: UDP-N-acetyl-α-D-glucosamine:α-D-mannosyl-(1→3)-β-D-mannosyl-glycoprotein 2-β-N-acetyl-D-glucosaminyltransferase (configuration-inverting)
Comments: The enzyme, found in plants and animals, participates in the processing of N-glycans in the Golgi apparatus. Its action is required before the other N-acetylglucosaminyltransferases involved in the process (GlcNAcT-II through VI) can act. While the natural substrate (produced by EC 3.2.1.113, mannosyl-oligosaccharide 1,2-α-mannosidase) is described here, the minimal substrate recognized by the enzyme is α-D-Man-(1→3)-β-D-Man-R.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 102576-81-8
References:
1.  Harpaz, N. and Schachter, H. Control of glycoprotein synthesis. Bovine colostrum UDP-N-acetylglucosamine:α-D-mannoside β2-N-acetylglucosaminyltransferase I. Separation from UDP-N-acetylglucosamine:α-D-mannoside β2-N-acetylglucosaminyltransferase II, partial purification, and substrate specificity. J. Biol. Chem. 255 (1980) 4885–4893. [PMID: 6445358]
2.  Mendicino, J., Chandrasekaran, E.V., Anumula, K.R. and Davila, M. Isolation and properties of α-D-mannose:β-1,2-N-acetylglucosaminyltransferase from trachea mucosa. Biochemistry 20 (1981) 967–976. [PMID: 6452163]
3.  Oppenheimer, C.L. and Hill, R.L. Purification and characterization of a rabbit liver α1→3 mannoside β1→2 N-acetylglucosaminyltransferase. J. Biol. Chem. 256 (1981) 799–804. [PMID: 6450208]
4.  Oppenheimer, C.L., Eckhardt, A.E. and Hill, R.L. The nonidentity of porcine N-acetylglucosaminyltransferases I and II. J. Biol. Chem. 256 (1981) 11477–11482. [PMID: 6457827]
5.  Miyagi, T. and Tsuiki, S. Studies on UDP-N-acetylglucosamine : α-mannoside β-N-acetylglucosaminyltransferase of rat liver and hepatomas. Biochim. Biophys. Acta 661 (1981) 148–157. [DOI] [PMID: 6170335]
6.  Schachter, H., Narasimhan, S., Gleeson, P. and Vella, G. Glycosyltransferases involved in elongation of N-glycosidically linked oligosaccharides of the complex or N-acetyllactosamine type. Methods Enzymol. 98 (1983) 98–134. [PMID: 6366476]
7.  Vella, G.J., Paulsen, H. and Schachter, H. Control of glycoprotein synthesis. IX. A terminal Man alphal-3Man β1- sequence in the substrate is the minimum requirement for UDP-N-acetyl-D-glucosamine: α-D-mannoside (GlcNAc to Man α1-3) β2-N-acetylglucosaminyltransferase I. Can. J. Biochem. Cell Biol. 62 (1984) 409–417. [PMID: 6235906]
8.  Unligil, U.M., Zhou, S., Yuwaraj, S., Sarkar, M., Schachter, H. and Rini, J.M. X-ray crystal structure of rabbit N-acetylglucosaminyltransferase I: catalytic mechanism and a new protein superfamily. EMBO J. 19 (2000) 5269–5280. [DOI] [PMID: 11032794]
[EC 2.4.1.101 created 1983, modified 2001 (EC 2.4.1.51 created 1972, part incorporated 1984), modified 2018]
 
 
EC 3.2.1.114     
Accepted name: mannosyl-oligosaccharide 1,3-1,6-α-mannosidase
Reaction: Man5GlcNAc3-[protein] + 2 H2O = Man3GlcNAc3-[protein] + 2 α-D-mannopyranose
For diagram of mannosyl-glycoprotein n-acetylglucosaminyltransferases, click here
Glossary: Man5GlcNAc3-[protein] = [β-D-GlcNAc-(1→2)-α-D-Man-(1→3)-{α-D-Man-(1→3)-[α-D-Man-(1→6)]-α-D-Man-(1→6)}-β-D-Man-(1→4)-β-D-GlcNAc-(1→4)-β-D-GlcNAc]-N-Asn-[protein]
Man3GlcNAc3-[protein] = {β-D-GlcNAc-(1→2)-α-D-Man-(1→3)-[α-D-Man-(1→6)]-β-D-Man-(1→4)-β-D-GlcNAc-(1→4)-β-D-GlcNAc}-N-Asn-[protein]
Other name(s): MAN2A1 (gene name); MAN2A2 (gene name); mannosidase II; exo-1,3-1,6-α-mannosidase; α-D-mannosidase II; α-mannosidase II; α1-3,6-mannosidase; GlcNAc transferase I-dependent α1,3[α1,6]mannosidase; Golgi α-mannosidase II; ManII; 1,3(1,6)-α-D-mannosidase; 1,3-(1,6-)mannosyl-oligosaccharide α-D-mannohydrolase; (1→3)-(1→6)-mannosyl-oligosaccharide α-D-mannohydrolase
Systematic name: (1→3)-(1→6)-mannosyl-oligosaccharide α-D-mannohydrolase (configuration-retaining)
Comments: The enzyme, found in plants and animals, participates in the processing of N-glycans in the Golgi apparatus. It removes two mannosyl residues, one linked by α1,3 linkage, and the other linked by α1,6 linkage, both of which are removed by the same catalytic site. The enzyme is sensitive to swainsonine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 82047-77-6
References:
1.  Tulsiani, D.R.P., Opheim, D.J. and Touster, O. Purification and characterization of α-D-mannosidase from rat liver golgi membranes. J. Biol. Chem. 252 (1977) 3227–3233. [PMID: 863880]
2.  Tabas, I. and Kornfeld, S. The synthesis of complex-type oligosaccharides. III. Identification of an α-D-mannosidase activity involved in a late stage of processing of complex-type oligosaccharides. J. Biol. Chem. 253 (1978) 7779–7786. [PMID: 212436]
3.  Harpaz, N. and Schachter, H. Control of glycoprotein synthesis. Processing of asparagine-linked oligosaccharides by one or more rat liver Golgi α-D-mannosidases dependent on the prior action of UDP-N-acetylglucosamine: α-D-mannoside β2-N-acetylglucosaminyltransferase I. J. Biol. Chem. 255 (1980) 4894–4902. [PMID: 6445359]
4.  Tulsiani, D.R.P., Hubbard, S.C., Robbins, P.W. and Touster, O. α-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. J. Biol. Chem. 257 (1982) 3660–3668. [PMID: 7061502]
5.  Moremen, K.W. and Robbins, P.W. Isolation, characterization, and expression of cDNAs encoding murine α-mannosidase II, a Golgi enzyme that controls conversion of high mannose to complex N-glycans. J. Cell Biol. 115 (1991) 1521–1534. [PMID: 1757461]
6.  Misago, M., Liao, Y.F., Kudo, S., Eto, S., Mattei, M.G., Moremen, K.W. and Fukuda, M.N. Molecular cloning and expression of cDNAs encoding human α-mannosidase II and a previously unrecognized α-mannosidase IIx isozyme. Proc. Natl. Acad. Sci. USA 92 (1995) 11766–11770. [DOI] [PMID: 8524845]
7.  van den Elsen, J.M., Kuntz, D.A. and Rose, D.R. Structure of Golgi α-mannosidase II: a target for inhibition of growth and metastasis of cancer cells. EMBO J. 20 (2001) 3008–3017. [DOI] [PMID: 11406577]
8.  Athanasopoulos, V.I., Niranjan, K. and Rastall, R.A. The production, purification and characterisation of two novel α-D-mannosidases from Aspergillus phoenicis. Carbohydr. Res. 340 (2005) 609–617. [DOI] [PMID: 15721331]
9.  Shah, N., Kuntz, D.A. and Rose, D.R. Golgi α-mannosidase II cleaves two sugars sequentially in the same catalytic site. Proc. Natl. Acad. Sci. USA 105 (2008) 9570–9575. [DOI] [PMID: 18599462]
10.  Rose, D.R. Structure, mechanism and inhibition of Golgi α-mannosidase II. Curr. Opin. Struct. Biol. 22 (2012) 558–562. [DOI] [PMID: 22819743]
[EC 3.2.1.114 created 1986, modified 2018]
 
 


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