抄録
Rat intestinal maltase and sucrase-isomaltase were isolated from the supernate after papain solubilisation of the brush border membrane, which was prepared by calcium precipitation, with repeated chromatographies of Sepharose 6 B and DEAE-cellulose columns for maltase or with those of Sepharose 6 B, DEAE-cellulose and Sephadex G-200 columns for sucrase-isomaltase. The level of purification of the original mucosal homogenate was approximately 220-fold in maltase and 130-fold in sucrase-isomaltase. The purity of both enzymes was recognized by the single band in 6% polyacrylamide gel electrophoresis and a single precipitation arc in immunoelectrophoresis with antiserum to the papain supernate. Double immunodiffusion of the purified enzymes against antisera, individually developed from the two purified enzymes, showed no cross-reactions, indicating the independence of the immunoreaction between these two enzymes.
The enzyme activities for maltose, lactose and sucrose were determined from the papain supernate and the enzyme protein were measured by rocket immunoelectrophoresis. Specific activities were determined from the combination of these two procedures. There were 12 units/ mg in maltase, 17 units/mg in lactase and 6 units/mg in sucrase-isomaltase. Although the enzyme activities of maltase and sucrase-isomaltase were detected in the intestinal extracts of the pups immediately after birth, only maltase was recognised immunochemically'at birth. Ten days after birth sucrase-isomaltase was detectable, The two activities increased with the age of the animals, and the specific activities for the enzyme proteins were 15 units/mg in maltase and 5. 5 units/mg in sucrase-isomaltase on the 21st day. These were similar to that found in the adult rats. The change of the specific activities of maltase and sucrase-isomaltase was followed throughout the whole day. Although the activities and enzyme proteins were greater during the feeding period (midnight) compared with the resting period (at noon), the specific activity of sucrase-isomaltase against the enzyme protein was significantly less at the feeding period than at the resting period, which suggested the presence of an ineffective enzyme at the feeding period.
