Purification and characterization of β-galactosidase-1 from Drosophila melanogaster

β-Galactosidase-1 (EC 3.2.1.23) from adult Drosophila melanogaster was purified over 5200-fold to apparent homogeneity. The purified enzyme is a glycoprotein and a homodimer with a native mol. wt of 160 kDa. It has a molecular activity of 35 p-nitrophenyl-β-d-galactopyranoside molecules hydrolyzed per second at 37°C, pH 6.0, and KM values of 1.26 ± 0.13 and 1.40 ± 0.10 mM for o- and p-nitrophenyl-β-d-galactopyranoside, respectively. β-Galactosidase-1 comprises less than 0.02% of total soluble protein corresponding on average to 2–3 ng/adult fly. Antiserum was prepared against the purified enzyme and its specificity was determined by analysis of proteins immunoprecipitated from a partially purified extract of adult flies.