CHARACTERIZATION OF INTESTINAL GAMMA-GLUCOAMYLASE DEFICIENCY IN CBA CA MICE/

In previous work, we found that CBA/Ca mice display only 20% of the ma ltase activity present in other mouse strains. In this study, we chara cterized more fully the maltase deficiency in CBA/Ca mice. Virtually a ll of the intestinal maltase activity of CBA/Ca mice was inactivated a t 50-degrees-C, indicating that it was due only to the sucrase-isomalt ase complex. High-performance liquid chromatographic analysis revealed that CBA/Ca mice had undetectable maltase activity displaying the mol ecular mass characteristic of murine gamma-glucoamylase (gamma-GA) (53 0 kDa). Gel electrophoretic analysis confirmed that CBA/Ca mice lacked maltase activity with molecular mass of 530 kDa corresponding to gamm a-GA. Two-dimensional electrophoretic analysis revealed that the gamma -GA deficiency in CBA/Ca mice was due to the failure to synthesize the enzyme and not to the synthesis of an inactive protein. Gamma-GA malt ase activity could not be induced in CBA/Ca mice by a diet rich in sta rch, whereas the activity of other disaccharidases were readily increa sed. Gamma-GA-deficient CBA/Ca mice appear to lack any gross metabolic abnormality resulting from this defect.