Expression, purification, crystallization and preliminary X-ray crystallographic analysis of human β-galactosidase.

β-D-Galactosidase (β-Gal) is an exoglycosidase that cleaves β-galactosides from glycoproteins, sphingolipids and keratan sulfate. This study reports the expression, purification, crystallization and preliminary X-ray crystallographic analysis of human lysosomal β-Gal. The sitting-drop vapour-diffusion method was used to crystallize β-Gal in complexes with its product galactose and with the inhibitor 1-deoxygalactonojirimycin. The resulting crystals were isomorphous and belonged to space group P2(1). The crystals of the β-Gal-galactose and the β-Gal-inhibitor complexes had unit-cell parameters a = 94.8, b = 116.1, c = 140.3 Å, β = 92.2° and a = 94.8, b = 116.0, c = 140.3 Å, β = 92.2°, respectively. Diffraction data were collected to 1.8 Å resolution for both crystals.