glycosyl hydrolase family 36 (GH36). GH36 enzymes occur in prokaryotes, eukaryotes, and archaea with a wide range of hydrolytic activities, including alpha-galactosidase, alpha-N-acetylgalactosaminidase, stachyose synthase, and raffinose synthase. All GH36 enzymes cleave a terminal carbohydrate moiety from a substrate that varies considerably in size, depending on the enzyme, and may be either a starch or a glycoprotein. GH36 members are retaining enzymes that cleave their substrates via an acid/base-catalyzed, double-displacement mechanism involving a covalent glycosyl-enzyme intermediate. Two aspartic acid residues have been identified as the catalytic nucleophile and the acid/base, respectively.

Melibiase. Glycoside hydrolase families GH27, GH31 and GH36 form the glycoside hydrolase clan GH-D. Glycoside hydrolase family 36 can be split into 11 families, GH36A to GH36K. This family includes enzymes from GH36A-B and GH36D-K and from GH27.

Alpha-galactosidase [Carbohydrate transport and metabolism].

glycosyl hydrolase family 31 (GH31). GH31 enzymes occur in prokaryotes, eukaryotes, and archaea with a wide range of hydrolytic activities, including alpha-glucosidase (glucoamylase and sucrase-isomaltase), alpha-xylosidase, 6-alpha-glucosyltransferase, 3-alpha-isomaltosyltransferase and alpha-1,4-glucan lyase. All GH31 enzymes cleave a terminal carbohydrate moiety from a substrate that varies considerably in size, depending on the enzyme, and may be either a starch or a glycoprotein. In most cases, the pyranose moiety recognized in subsite -1 of the substrate binding site is an alpha-D-glucose, though some GH31 family members show a preference for alpha-D-xylose. Several GH31 enzymes can accommodate both glucose and xylose and different levels of discrimination between the two have been observed. Most characterized GH31 enzymes are alpha-glucosidases. In mammals, GH31 members with alpha-glucosidase activity are implicated in at least three distinct biological processes. The lysosomal acid alpha-glucosidase (GAA) is essential for glycogen degradation and a deficiency or malfunction of this enzyme causes glycogen storage disease II, also known as Pompe disease. In the endoplasmic reticulum, alpha-glucosidase II catalyzes the second step in the N-linked oligosaccharide processing pathway that constitutes part of the quality control system for glycoprotein folding and maturation. The intestinal enzymes sucrase-isomaltase (SI) and maltase-glucoamylase (MGAM) play key roles in the final stage of carbohydrate digestion, making alpha-glucosidase inhibitors useful in the treatment of type 2 diabetes. GH31 alpha-glycosidases are retaining enzymes that cleave their substrates via an acid/base-catalyzed, double-displacement mechanism involving a covalent glycosyl-enzyme intermediate. Two aspartic acid residues have been identified as the catalytic nucleophile and the acid/base, respectively.

Alpha amylase catalytic domain found in archaeal and bacterial Alpha-amylases (also called 1,4-alpha-D-glucan-4-glucanohydrolase). AmyA (EC 3.2.1.1) catalyzes the hydrolysis of alpha-(1,4) glycosidic linkages of glycogen, starch, related polysaccharides, and some oligosaccharides. This group includes firmicutes, bacteroidetes, and proteobacteria. The Alpha-amylase family comprises the largest family of glycoside hydrolases (GH), with the majority of enzymes acting on starch, glycogen, and related oligo- and polysaccharides. These proteins catalyze the transformation of alpha-1,4 and alpha-1,6 glucosidic linkages with retention of the anomeric center. The protein is described as having 3 domains: A, B, C. A is a (beta/alpha) 8-barrel; B is a loop between the beta 3 strand and alpha 3 helix of A; C is the C-terminal extension characterized by a Greek key. The majority of the enzymes have an active site cleft found between domains A and B where a triad of catalytic residues (Asp, Glu and Asp) performs catalysis. Other members of this family have lost the catalytic activity as in the case of the human 4F2hc, or only have 2 residues that serve as the catalytic nucleophile and the acid/base, such as Thermus A4 beta-galactosidase with 2 Glu residues (GH42) and human alpha-galactosidase with 2 Asp residues (GH31). The family members are quite extensive and include: alpha amylase, maltosyltransferase, cyclodextrin glycotransferase, maltogenic amylase, neopullulanase, isoamylase, 1,4-alpha-D-glucan maltotetrahydrolase, 4-alpha-glucotransferase, oligo-1,6-glucosidase, amylosucrase, sucrose phosphorylase, and amylomaltase.

Structureof alpha-galactosidase from Lactobacillus acidophilus NCFM, PtCl4 derivative [Lactobacillus acidophilus NCFM],2XN0_B Structure of alpha-galactosidase from Lactobacillus acidophilus NCFM, PtCl4 derivative [Lactobacillus acidophilus NCFM],2XN1_A Structure of alpha-galactosidase from Lactobacillus acidophilus NCFM with TRIS [Lactobacillus acidophilus NCFM],2XN1_B Structure of alpha-galactosidase from Lactobacillus acidophilus NCFM with TRIS [Lactobacillus acidophilus NCFM],2XN1_C Structure of alpha-galactosidase from Lactobacillus acidophilus NCFM with TRIS [Lactobacillus acidophilus NCFM],2XN1_D Structure of alpha-galactosidase from Lactobacillus acidophilus NCFM with TRIS [Lactobacillus acidophilus NCFM]

Structureof alpha-galactosidase from Lactobacillus acidophilus NCFM with galactose [Lactobacillus acidophilus NCFM]

Crystalstructure of GH36 alpha-galactosidase AgaA from Geobacillus stearothermophilus [Geobacillus stearothermophilus],4FNR_B Crystal structure of GH36 alpha-galactosidase AgaA from Geobacillus stearothermophilus [Geobacillus stearothermophilus],4FNR_C Crystal structure of GH36 alpha-galactosidase AgaA from Geobacillus stearothermophilus [Geobacillus stearothermophilus],4FNR_D Crystal structure of GH36 alpha-galactosidase AgaA from Geobacillus stearothermophilus [Geobacillus stearothermophilus]

Crystalstructure of GH36 alpha-galactosidase AgaB from Geobacillus stearothermophilus [Geobacillus stearothermophilus]

Crystalstructure of GH36 alpha-galactosidase AgaA A355E D548N from Geobacillus stearothermophilus in complex with raffinose [Geobacillus stearothermophilus],4FNT_B Crystal structure of GH36 alpha-galactosidase AgaA A355E D548N from Geobacillus stearothermophilus in complex with raffinose [Geobacillus stearothermophilus],4FNT_C Crystal structure of GH36 alpha-galactosidase AgaA A355E D548N from Geobacillus stearothermophilus in complex with raffinose [Geobacillus stearothermophilus],4FNT_D Crystal structure of GH36 alpha-galactosidase AgaA A355E D548N from Geobacillus stearothermophilus in complex with raffinose [Geobacillus stearothermophilus]

Alpha-galactosidase Mel36A OS=Lactobacillus acidophilus (strain ATCC 700396 / NCK56 / N2 / NCFM) OX=272621 GN=melA PE=1 SV=1

Alpha-galactosidase AgaA OS=Geobacillus stearothermophilus OX=1422 GN=agaA PE=1 SV=1

Alpha-galactosidase 1 OS=Pediococcus pentosaceus OX=1255 GN=agaR PE=3 SV=1

Alpha-galactosidase C OS=Emericella nidulans (strain FGSC A4 / ATCC 38163 / CBS 112.46 / NRRL 194 / M139) OX=227321 GN=aglC PE=1 SV=1

Alpha-galactosidase OS=Escherichia coli OX=562 GN=rafA PE=1 SV=1