N-terminal catalytic domain of class II alpha-mannosidases and similar proteins; glycoside hydrolase family 38 (GH38). Alpha-mannosidases (EC 3.2.1.24) are extensively found in eukaryotes and play important roles in the processing of newly formed N-glycans and in degradation of mature glycoproteins. A deficiency of this enzyme causes the lysosomal storage disease alpha-mannosidosis. Many bacterial and archaeal species also possess putative alpha-mannosidases, but their activity and specificity is largely unknown. Based on different functional characteristics and sequence homology, alpha-mannosidases have been organized into two classes (class I, belonging to glycoside hydrolase family 47, and class II, belonging to glycoside hydrolase family 38). Members of this family corresponds to class II alpha-mannosidases (alphaMII), which contain intermediate Golgi alpha-mannosidases II, acidic lysosomal alpha-mannosidases, animal sperm and epididymal alpha -mannosidases, neutral ER/cytosolic alpha-mannosidases, and some putative prokaryotic alpha-mannosidases. AlphaMII possess a-1,3, a-1,6, and a-1,2 hydrolytic activity, and catalyzes the degradation of N-linked oligosaccharides. The N-terminal catalytic domain of alphaMII adopts a structure consisting of parallel 7-stranded beta/alpha barrel. Members in this family are retaining glycosyl hydrolases of family GH38 that employs a two-step mechanism involving the formation of a covalent glycosyl enzyme complex. Two carboxylic acids positioned within the active site act in concert: one as a catalytic nucleophile and the other as a general acid/base catalyst.

Glycosyl hydrolases family 38 N-terminal domain. Glycosyl hydrolases are key enzymes of carbohydrate metabolism.

N-terminal catalytic domain of endoplasmic reticulum(ER)/cytosolic class II alpha-mannosidases; glycoside hydrolase family 38 (GH38). The subfamily is represented by Saccharomyces cerevisiae vacuolar alpha-mannosidase Ams1, rat ER/cytosolic alpha-mannosidase Man2C1, and similar proteins. Members in this family share high sequence similarity. None of them have any classical signal sequence or membrane spanning domains, which are typical of sorting or targeting signals. Ams1 functions as a second resident vacuolar hydrolase in S. cerevisiae. It aids in recycling macromolecular components of the cell through hydrolysis of terminal, non-reducing alpha-d-mannose residues. Ams1 utilizes both the cytoplasm to vacuole targeting (Cvt, nutrient-rich conditions) and autophagic (starvation conditions) pathways for biosynthetic delivery to the vacuole. Man2C1is involved in oligosaccharide catabolism in both the ER and cytosol. It can catalyze the cobalt-dependent cleavage of alpha 1,2-, alpha 1,3-, and alpha 1,6-linked mannose residues. Members in this family are retaining glycosyl hydrolases of family GH38 that employs a two-step mechanism involving the formation of a covalent glycosyl-enzyme complex. Two carboxylic acids positioned within the active site act in concert: one as a catalytic nucleophile and the other as a general acid/base catalyst.

N-terminal catalytic domain of putative prokaryotic class II alpha-mannosidases; glycoside hydrolase family 38 (GH38). This mainly bacterial subfamily corresponds to a group of putative class II alpha-mannosidases, including various proteins assigned as alpha-mannosidases, Streptococcus pyogenes (SpGH38) encoded by ORF spy1604. Escherichia coli MngB encoded by the mngB/ybgG gene, and Thermotoga maritime TMM, and similar proteins. SpGH38 targets alpha-1,3 mannosidic linkages. SpGH38 appears to exist as an elongated dimer and display alpha-1,3 mannosidase activity. It is active on disaccharides and some aryl glycosides. SpGH38 can also effectively deglycosylate human N-glycans in vitro. MngB exhibits alpha-mannosidase activity that catalyzes the conversion of 2-O-(6-phospho-alpha-mannosyl)-D-glycerate to mannose-6-phosphate and glycerate in the pathway which enables use of mannosyl-D-glycerate as a sole carbon source. TMM is a homodimeric enzyme that hydrolyzes p-nitrophenyl-alpha-D-mannopyranoside, alpha -1,2-mannobiose, alpha -1,3-mannobiose, alpha -1,4-mannobiose, and alpha -1,6-mannobiose. The GH38 family contains retaining glycosyl hydrolases that employ a two-step mechanism involving the formation of a covalent glycosyl enzyme complex. Two carboxylic acids positioned within the active site act in concert: one as a catalytic nucleophile and the other as a general acid/base catalyst. Divalent metal ions, such as zinc or cobalt ions, are suggested to be required for the catalytic activities of typical class II alpha-mannosidases. However, TMM requires the cobalt or cadmium for its activity. The cadmium ion dependency is unique to TMM. Moreover, TMM is inhibited by swainsonine but not 1-deoxymannojirimycin, which is in agreement with the features of cytosolic alpha-mannosidase.

N-terminal catalytic domain of SPGH38, a putative alpha-mannosidase of Streptococcus pyogenes, and its prokaryotic homologs; glycoside hydrolase family 38 (GH38). The subfamily is represented by SpGH38 of Streptococcus pyogenes, which has been assigned as a putative alpha-mannosidase, and is encoded by ORF spy1604. SpGH38 appears to exist as an elongated dimer and display alpha-1,3 mannosidase activity. It is active on disaccharides and some aryl glycosides. SpGH38 can also effectively deglycosylate human N-glycans in vitro. A divalent metal ion, such as a zinc ion, is required for its activity. SpGH38 is inhibited by swainsonine. The absence of any secretion signal peptide suggests that SpGH38 may be intracellular.

Structureof S.pombe alpha-mannosidase Ams1 [Schizosaccharomyces pombe 972h-],6LZ1_B Structure of S.pombe alpha-mannosidase Ams1 [Schizosaccharomyces pombe 972h-],6LZ1_C Structure of S.pombe alpha-mannosidase Ams1 [Schizosaccharomyces pombe 972h-],6LZ1_D Structure of S.pombe alpha-mannosidase Ams1 [Schizosaccharomyces pombe 972h-]

ChainA, Alpha-mannosidase,ZZ-type zinc finger-containing protein P35G2.11c,Maltose/maltodextrin-binding periplasmic protein [synthetic construct],7DD9_C Chain C, Alpha-mannosidase,ZZ-type zinc finger-containing protein P35G2.11c,Maltose/maltodextrin-binding periplasmic protein [synthetic construct],7DD9_E Chain E, Alpha-mannosidase,ZZ-type zinc finger-containing protein P35G2.11c,Maltose/maltodextrin-binding periplasmic protein [synthetic construct],7DD9_G Chain G, Alpha-mannosidase,ZZ-type zinc finger-containing protein P35G2.11c,Maltose/maltodextrin-binding periplasmic protein [synthetic construct]

Structureof the Streptococcus pyogenes family GH38 alpha-mannosidase [Streptococcus pyogenes M1 GAS],2WYH_B Structure of the Streptococcus pyogenes family GH38 alpha-mannosidase [Streptococcus pyogenes M1 GAS],2WYI_A Structure of the Streptococcus pyogenes family GH38 alpha-mannosidase complexed with swainsonine [Streptococcus pyogenes M1 GAS],2WYI_B Structure of the Streptococcus pyogenes family GH38 alpha-mannosidase complexed with swainsonine [Streptococcus pyogenes M1 GAS]

Mannosylglycerate hydrolase OS=Escherichia coli (strain K12) OX=83333 GN=mngB PE=1 SV=2

Alpha-mannosidase OS=Schizosaccharomyces pombe (strain 972 / ATCC 24843) OX=284812 GN=ams1 PE=1 SV=1

Alpha-mannosidase G OS=Dictyostelium discoideum OX=44689 GN=manG PE=1 SV=1

Alpha-mannosidase 2C1 OS=Homo sapiens OX=9606 GN=MAN2C1 PE=1 SV=1