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Beta-galactosidase

β-galactosidase
Beta-galactosidase (1tg7).png
β-galactosidase from Penicillum sp.
Identifiers
EC number 3.2.1.23
CAS number 9031-11-2
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 / EGO
galactosidase, beta 1
Identifiers
Symbol GLB1
Alt. symbols ELNR1
Entrez 2720
HUGO 4298
OMIM 230500
RefSeq NM_000404
UniProt P16278
Other data
Locus Chr. 3 p22.3

β-galactosidase, also called beta-gal or β-gal, is a glycoside hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides through the breaking of a glycosidic bond. β-galactosides include carbohydrates containing galactose where the glycosidic bond lies above the galactose molecule. Substrates of different β-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins.

β-galactosidase is an exoglycosidase which hydrolyzes the β-glycosidic bond formed between a galactose and its organic moiety. It may also cleave fucosides and arabinosides but with much lower efficiency. It is an essential enzyme in the human body. Deficiencies in the protein can result in galactosialidosis or Morquio B syndrome. In E. coli, the lacZ gene is the structural gene for β-galactosidase; which is present as part of the inducible system lac operon which is activated in the presence of lactose when glucose level is low. β-galactosidase synthesis stops when glucose levels are sufficient.

Beta-galactosidase has many homologues based on similar sequences. A few are evolved beta-galactosidase (EBG), beta-glucosidase, 6-phospho-beta-galactosidase, beta-mannosidase, and lactase-phlorizin hydrolase. Although they may be structurally similar, they all have different functions. Beta-gal is inhibited by L-ribose, non-competitive inhibitor iodine, and competitive inhibitors phenylthyl thio-beta-D-galactoside (PETG), D-galactonolactone, isopropyl thio-beta-D-galactoside (IPTG), and galactose.


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Wikipedia

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