Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 6/1/2005
Publication Date: 10/1/2005
Citation: Nichols, B.L., Avery, S., Sen, P., Robayo, C., Quezada-Calvillo, R., Wattler, S., Nehls, M.C., Luginbuehl, U., Sterchi, E. 2006. Secreted maltase-glucoamylase is upregulated in membrane maltase-glucoamylase null mice. In: Naim HY, Zimmer KP, editors. The Brush Border Membrane: From Molecular Cell Biology to Clinical Pathology. Heilbronn, Germany: SPS Verlagsgesellschaft. p. 214-224. Interpretive Summary:
Technical Abstract: The known mammalian brush-border glucohydrolases are membrane-bound, small intestine lumenal enzymes that digest dietary starches and sugars into monosaccharides for absorption. The phenotype of maltase-glucoamylase deficiency is not understood. To address this, we ablated membrane-bound maltase-glucoamylase (Mgamme) in the mouse. This was accomplished with a cassette that inserted a stop codon within exon 2, the membrane-binding domain. Here we report the discovery of a novel soluble maltase-glucoamylase peptide (Mgamso). Membrane bound maltase-glucoamylase was absent by Western blot in Mgamme null mice, but soluble maltase-glucoamylase activity was present in both small and large bowel of membrane maltase-glucoamylase null mice. Sequencing of small intestinal cDNA from Mgamme null mice confirmed absence of maltase-glucoamylase exon 2. Sequencing of cDNA from Mgamme wild type mice revealed a low level of the 1,3 spliceoform message. The copy number of the 1,3 spliceoform was increased by 8 fold in the Mgamme null mouse.