MetaCyc

Parent Class:

EC-Numbers → 3 -- Hydrolases → 3.2 -- Glycosylases → 3.2.1 -- Glycosidases, i.e. enzymes hydrolyzing O- and S-glycosyl compounds

Synonyms: lactase (ambiguous), β-lactosidase, maxilact, hydrolact, β-D-lactosidase, S 2107, lactozym, trilactase, β-D-galactanase, oryzatym, sumiklat

Systematic Name: β-D-galactoside galactohydrolase

Unification Links: BRENDA:3.2.1.23, ENZYME:3.2.1.23, IUBMB-ExplorEnz:3.2.1.23

Reaction:
a β-D-galactoside + H₂O → a non galactosylated galactose acceptor + D-galactopyranose

Unofficial Reactions:
XLLG xyloglucan oligosaccharide + 2 H₂O → XXXG xyloglucan oligosaccharide + 2 D-galactopyranose,
XLXG xyloglucan oligosaccharide + H₂O → XXXG xyloglucan oligosaccharide + D-galactopyranose,
XXLG xyloglucan oligosaccharide + H₂O → XXXG xyloglucan oligosaccharide + D-galactopyranose,
4-nitrophenyl-β-D-galactoside + H₂O → 4-nitrophenol + D-galactopyranose + H⁺

Enzymes and Genes:
β-galactosidase: LacZ ( Sinorhizobium meliloti Rm2011 )
β-galactosidase: lacL, lacM ( Limosilactobacillus reuteri )
β-galactosidase: lacA ( Aspergillus niger )
β-galactosidase: bga1 ( Trichoderma reesei )

Summary:
This enzyme catalyzes the hydrolysis of terminal non-reducing β-D-galactose residues in β-D-galactosides. Some enzymes in this group hydrolyse α-L-arabinosides; some animal enzymes also hydrolyse β-D-fucosides and β-D-glucosides; cf. EC 3.2.1.108, lactase.

Citations: [Monod52, Kuby53, Landman57, Wallenfels60, Blakely69, Asp69, Kuo78]