Characterization of intestinal γ-glucoamylase deficiency in CBA/Ca mice
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abstract
In previous work, we found that CBA/Ca mice display only 20%25 of the maltase activity present in other mouse strains. In this study, we characterized more fully the maltase deficiency in CBA/Ca mice. Virtually all of the intestinal maltase activity of CBA/Ca mice was inactivated at 50°C, indicating that it was due only to the sucrase-isomaltase complex. High- performance liquid chromatographic analysis revealed that CBA/Ca mice had undetectable maltase activity displaying the molecular mass characteristic of murine γ-glucoamylase (γ-GA) (530 kDa). Gel electrophoretic analysis confirmed that CBA/Ca mice lacked maltase activity with molecular mass of 530 kDa corresponding to γ-GA. Two-dimensional electrophoresis analysis revealed that the γ-GA deficiency in CBA/Ca mice was due to the failure to synthesize the enzyme and not to the synthesis of an inactive protein. γ-GA maltase activity could not be induced in CBA/Ca mice by a diet rich in starch, whereas the activity of other disaccharidases were readily increased. γ-GA- deficient CBA/Ca mice appear to lack any gross metabolic abnormality resulting from this defect.
