Monoclonal antibodies to renal brush border membrane maltase: age-associated antigenic alterations.

Monoclonal antibodies to maltase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) from young adult and aged rats were prepared by the hybridoma technique. Four cell lines producing antibodies of the IgG1 subclass to maltase were established. Two, designated 1F12E1 and 8B1G6, produced monoclonal antibodies specific for the catalytically active form of the enzyme found predominantly in enzyme preparations from young animals. The other two clones designated 7G10H3 and 2E1C10 produced monoclonal antibodies that reacted exclusively with an enzymatically inactive form of maltase found mostly in enzyme preparations from aged rats. The increased prevalence of an inactive form of the enzyme in the old rat accounts for the decreased maltase-specific activity previously reported in the senescent rat. The active and inactive maltase species were separated by immunoaffinity chromatography by using the monoclonal antibodies as ligands. The separated forms of the enzyme were not distinguished by NaDodSO4/polyacrylamide gel electrophoresis, peptide mapping of the CNBr-cleaved proteins, and the NH2-terminal residues of these peptides. This study demonstrates the presence of an altered, antigenically distinct enzyme in senescent animals. Critical issues on the mechanism of the aging process may be addressed by application of these findings.