Isolation of a beta-galactosidase from chicken liver

In search of a beta-galactosidase which specifically hydrolyses beta 1----3 bound galactose residues in galacto-glycoconjugates, an acid beta-galactosidase from chicken liver was investigated. The isolation procedure involved ammonium sulphate precipitation followed by lectin chromatography on Con A-Sepharose 4B, ion-exchange chromatography on DEAE-cellulose, gel filtration on Sepharose 6B and affinity chromatography on p-aminophenyl-thio-beta-D-galactoside-agarose. The beta-galactosidase was purified 3000-fold with 11% recovery of enzyme activity. The purified protein showed an apparent molecular mass of above 200000 in SDS-polyacrylamide gel electrophoresis. A few minor bands were also present. The reduced and denatured beta-galactosidase migrated as a single major band with an apparent molecular mass of 67000. The enzyme released galactose from lactose and from the synthetic substrates Gal beta 1----3Gal, Gal beta 1----6Gal and Gal beta 1----3Ara. However, the enzyme did not release galactose from the snail gland galactans and the high molecular weight galacto-glycoconjugates and it did not hydrolyse the peanut agglutinin receptor of the red blood cell membrane.