Evidence for a possible regulatory gene (Suc-1) controlling sucrase expression in mouse intestine.

Assays for sucrase carried out on intestinal sonicates prepared from 18 different strains of mice revealed a threefold variation in specific activity, the values for CBA/Ca mice being significantly less than for any other strain. Further comparison of the CBA/Ca versus the C57BL/6J mouse showed this deficiency, which became established 2-4 weeks after birth, to apply to isomaltase as well as sucrase but not to maltase or trehalase. Backcross experiments indicated that this deficiency in sucrase activity was inherited as a single codominantly expressed genetic factor. The ability of the CBA/Ca mouse to regulate sucrase activity in response to changes in diet was also reduced compared to that of the C57BL/6J mouse. No difference could be detected in the affinity of sucrase for its substrate or in the ability of heat to denature sucrase prepared from CBA/Ca and C57BL/6J mice. It is suggested that part of the regulatory region of the gene coding for sucrase-isomaltase is modified in the CBA/Ca mouse and that this locus should be given the notation Suc-1 for future reference.