CHARACTERIZATION OF PARTIALLY PURIFIED ALPHA-GLUCOSIDASE IN THE INSOLUBLE FRACTION OF BOVINE CRYSTALLINE LENS

Two fractions of neutral alpha-glucosidase were partially purified fro m the insoluble fraction of bovine lens. This is the first report of s uch an event to the best of our knowledge. The apparent native molecul ar weights of these fractions were 121 kDa (fraction-I) and 254 kDa (f raction-II). Both fractions contained three polypeptides with molecula r weights of 21, 25 and 30 kDa, although the proportion of these pepti des was different in both fractions. The optimal pH of fraction-I and fraction-II was pH 6.0 and 6.5, and the optimal temperature for both f ractions was approximately 50 degrees C. The K-m values of fractions-I and -II for 4-methylumbelliferyl-alpha-glucopyranoside were 0.086, an d 0.192 mM. The activities of these enzymes were inhibited strongly by HgCl2 and slightly by D-iodoacetic acid, but not by D-turanose. From this, we suggest that the enzyme in the insoluble fraction of bovine l ens may be a cytoplasmic neutral alpha-glucosidase which binds to the cell membrane.