Α-Galactosidase

This article is about the enzyme. For the carbohydrate commonly called "alpha gal", see Galactose-alpha-1,3-galactose.

α-Galactosidase ( EC 3.2.1.22, α-GAL, α-GAL A; systematic name α-D-galactoside galactohydrolase) is a glycoside hydrolase enzyme that catalyses the following reaction:^[1]

Hydrolysis of terminal, non-reducing α-D-galactose residues in α-D-galactosides, including galactose oligosaccharides, galactomannans and galactolipids

α-Galactosidase
α-Galactosidase tetramer in Mortierella vinacea
Identifiers
EC no.	3.2.1.22
CAS no.	9025-35-8
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

It catalyzes many catabolic processes, including cleavage of glycoproteins, glycolipids, and polysaccharides.

The enzyme is encoded by the GLA gene.^[2]

Function

This enzyme is a homodimeric glycoprotein that hydrolyses the terminal α-galactosyl moieties from glycolipids and glycoproteins. It predominantly hydrolyzes ceramide trihexoside, and it can catalyze the hydrolysis of melibiose into galactose and glucose.^{[citation needed]}

Reaction mechanism

A double displacement reaction mechanism of α-GAL's catalytic action.The ligand (black) when bound in the active site of the enzyme (blue). The two key amino acid residues in the active site are Asp-170 and Asp-231. First, Asp-170 performs a nucleophilic attack on the glycosidic bond to release the terminal α-galactose molecule from the ligand. Then, Asp-231 serves as an acid to remove a proton from water, making it more nucleophilic to attack the galactose-Asp complex and release α-galactose from the active site.^[3][4][5]

Applications

α-Galactosidase from Aspergillus niger is the active ingredient in Beano, a dietary supplement for bloating and flatulence.^[6][7]

Recombinant α-galactosidase made by baker's yeast is approved in Europe as a feed additive intended to make poultry food more digestible.^[8]

See also

• β-galactosidase
• Migalastat, a drug targeting α-galactosidase
• Classification of α-galactosidases (according to CAZy)