Murine intestinal disaccharidases: Identification of structural variants of sucrase-isomaltase complex

This study was directed to determine the extent of variability in structure or expression of intestinal disaccharidases [γ-glucoamylase (γ- GA), sucrase-isomaltase (SI), and lactase] between different strains of mice. Reduced levels of sucrase activity (~20 U/g of protein) were observed in three strains of mice belonging to the CBA/Ca lineage. Four other strains of mice analyzed exhibited higher levels of sucrase activity (~50 U/g of protein). Decreased levels of sucrase in CBA/Ca mice were not associated with decreased levels of activity associated with the isomaltase subunit or with decreased levels of SI mRNA expression. High-performance liquid chromatographic gel filtration, heat inactivation, and kinetic analysis indicated that the differences between strains in sucrase activity might be attributed to structural differences in the sucrase subunit of the SI complex, thus rendering it more susceptible to cleavage and inactivation. However, no differences in kinetic properties of the sucrase subunit were observed between strains. Murine γ-GA was found to account for a greater proportion of maltase activity (~70%25) than that observed in other species (i.e., ~20%25). In addition, CBA/Ca mice were found to be deficient in intestinal maltase activity (~60 U/g) compared with the other strains studied (~300 U/g).

genetic variation; inbred strains of mice; molecular structure; small intestine alpha glucosidase; disaccharidase; glucan 1,4 alpha glucosidase; intestine enzyme; lactase; messenger RNA; oligo 1,6 glucosidase; palatinose; sucrase; sucrase isomaltase; animal tissue; article; enzyme activity; enzyme structure; enzyme substrate; high performance liquid chromatography; Michaelis constant; mouse; mouse strain; nonhuman; priority journal; thermal exposure

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