Glycoside hydrolase 97. This domain is the catalytic region of the bacterial glycosyl-hydrolase family 97. This central part of the GH97 family protein sequences represents a typical and complete (beta/alpha)8-barrel or catalytic TIM-barrel type domain. The N- and C-terminal parts of the sequences, mainly consisting of beta-strands, form two additional non-catalytic domains. In all known glycosidases with the (beta-alpha)8-barrel fold, the amino acid residues at the active site are located on the C-termini of the beta-strands.

Glycosyl-hydrolase 97 N-terminal. This N-terminal domain of glycosyl-hydrolase-97 contributes part of the active site pocket. It is also important for contact with the catalytic and C-terminal domains of the whole.

Glycosyl-hydrolase 97 C-terminal, oligomerization. Glycosyl-hydrolase-97 is made up of three tightly linked and highly conserved globular domains. The C-terminal domain is found to be necessary for oligomerization of the whole molecule in order to create the active-site pocket and the Ca++-binding site.

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.

Crystalstructure of BT1871 retaining glycosidase [Bacteroides thetaiotaomicron],3A24_B Crystal structure of BT1871 retaining glycosidase [Bacteroides thetaiotaomicron]

Mutant(D415G) GH97 alpha-galactosidase in complex with Gal-Lac [Bacteroides thetaiotaomicron VPI-5482],5E1Q_B Mutant (D415G) GH97 alpha-galactosidase in complex with Gal-Lac [Bacteroides thetaiotaomicron VPI-5482]

AGlycoside Hydrolase Family 97 enzyme R171K variant from Pseudoalteromonas sp. strain K8 [Pseudoalteromonas sp. K8]

AGlycoside Hydrolase Family 97 enzyme from Pseudoalteromonas sp. strain K8 [Pseudoalteromonas sp. K8],5HQA_A A Glycoside Hydrolase Family 97 enzyme in complex with Acarbose from Pseudoalteromonas sp. strain K8 [Pseudoalteromonas sp. K8]

AGlycoside Hydrolase Family 97 enzyme (E480Q) in complex with Panose from Pseudoalteromonas sp. strain K8 [Pseudoalteromonas sp. K8]

Retaining alpha-galactosidase OS=Bacteroides thetaiotaomicron (strain ATCC 29148 / DSM 2079 / JCM 5827 / CCUG 10774 / NCTC 10582 / VPI-5482 / E50) OX=226186 GN=BT_1871 PE=1 SV=1

Probable retaining alpha-galactosidase OS=Streptomyces bingchenggensis (strain BCW-1) OX=749414 GN=SBI_01652 PE=3 SV=1

Glucan 1,4-alpha-glucosidase SusB OS=Bacteroides thetaiotaomicron (strain ATCC 29148 / DSM 2079 / JCM 5827 / CCUG 10774 / NCTC 10582 / VPI-5482 / E50) OX=226186 GN=susB PE=1 SV=1