Alpha-mannosidase [Carbohydrate transport and metabolism]

Alpha-mannosidase [Carbohydrate transport and metabolism]

N-terminal catalytic domain of mammalian cytosolic alpha-mannosidase Man2C1 and similar proteins; glycoside hydrolase family 38 (GH38). The subfamily corresponds to cytosolic alpha-mannosidase Man2C1 (also known as ER-mannosidase II or neutral/cytosolic mannosidase), mainly found in various vertebrates, and similar proteins. Man2C1 plays an essential role in the catabolism of cytosolic free oligomannosides derived from dolichol intermediates and the degradation of newly synthesized glycoproteins in ER or cytosol. It can catalyze the cleavage of alpha 1,2-, alpha 1,3-, and alpha 1,6-linked mannose residues. Man2C1 is a cobalt-dependent enzyme belonging to alpha-mannosidase class II. It has a neutral pH optimum and is strongly inhitibed by furanose analogs swainsonine (SW) and 1,4-dideoxy-1,4-imino-D-mannitol (DIM), moderately by deoxymannojirimycin (DMM), but not by kifunensine (KIF). DMM and KIF, both pyranose analogs, are normally known to inhibit class I alpha-mannosidase.

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.