Beta-glucosidase activity in porcine epidermis.

One of the final steps in epidermal differentiation is the conversion of glucosylceramides to ceramides, which presumably is mediated by a beta-glucosidase activity. In the present manuscript, it is demonstrated that pig epidermis contains beta-glucosidase activity which is 3.3-times greater than alpha-glucosidase and 5-times greater than beta-galactosidase. This beta-glucosidase was found to be maximally active between pH 3.0 and essentially inactive at pH 9.0. In a standard assay, a disk of epidermis (8 mg dry weight) was submerged in 1 ml of 50 mM acetate buffer (pH 4.7) containing 150 mM NaCl and 15 mM p-nitrophenyl-beta-D-glucopyranoside at room temperature. Reaction was stopped by addition of 4 ml of 100 mM (pH 9.0) borate buffer and the supernatant was transferred to a separate tube. The nitrophenylate anion was then measured spectrophotometrically at a wavelength of 405 nm. Under these conditions, product formation was linear for at least 90 min and an apparent Km of 244 microM was estimated for the synthetic substrate. When the amount of epidermis in the assay was varied, the formation of product per unit of time remained proportional to the amount of epidermis. The level of beta-glucosidase activity was enhanced slightly by the inclusion of sodium taurocholate.