Heterogeneity and some properties of beta-galactosidase from newborn rat epidermis

Two forms of beta-galactosidase from newborn rat epidermis could be separated by DEAE-cellulose chromatography. Both enzymes showed similar enzymic properties. They had a pH optimum around 3.5--4.5 and the optimal temperature of these enzymes was approximately 60 degrees C. They were not affected by divalent cations, ethylenediaminetetraacetic acid(EDTA) and 2-mercaptoethanol(2-ME), while rho-chloromercuribenzoic acid (PCMB) was a strong inhibitor for each enzyme. These enzymes showed the same Km value (1.25 x 10(-4) M) towards 4-methylumbelliferyl-beta-D-galactoside. However they had different isoelectric points at pH 6.3 and 9.0, respectively. Six different forms of beta-galactosidase activity were found by using isoelectric focusing. When the crude extract was incubated with neuraminidase before electrofocusing, the acidic forms of the enzyme were largely lost and converted to more basic forms without loss of the total activity. This finding suggests the glycoprotein nature of newborn rat epidermal beta-galactosidase.