Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2007
Publication Date: 6/1/2007
Citation: Nichols, B.L., Robayo-Torres, C.C., Ao, Z., Hamaker, B.R., Brayer, G.D., Sterchi, E.E., Quezada-Calvillo, R. 2007. Effect of mouse maltase-glucoamylase (Mgam) knockout on starch digestion to glucose [abstract]. Journal of Federation of American Societies for Experimental Biology. 21(5):A177. Interpretive Summary:
Technical Abstract: Digestion of starch requires activities provided by six different alpha-glucosidase enzymes. Two activities are luminal alpha-amylases (AMY). Four activities are mucosal activities described as maltases. Two of the activities are associated with sucrase-isomaltase (Si) activities. Two activities are named Mgam. We knocked out (KO) the Mgam gene to determine its role in digestion of starch to glucose in mice. The activities of Mgam KO null (N) and wild-type (WT) jejunum were assayed, with added recombinant AMY, using starch substrates and acarbose. Glucose release was measured by glucose-oxidase assay. Antibody for C-terminus was used for Western blots (WB). Oligomers of maltodextrin (MDx) were analyzed by MALDI-TOF before and after digestion to limit dextrin (LDx) with AMY. Mgam was present in WT but absent in N by WB. Jejunal activities for MDx, LDx, and maltose (M) were reduced in N. The Km of N for M and MDx was 5 X slower. alpha-Glucogenesis from MDx substrate was 20 X faster in WT. alpha-Amylase amplified by 3 X mucosal activity for MDx, but not LDx. LDx had more short oligomers. Acarbose Ki for M and MDx in WT was 7X stronger than N. Mgam KO reduced mucosal alpha-glucogenesis by 20 X. alpha-Amylase had little activity but amplified N and WT mucosal activity 3X. WT Mgam determined maximal rates of normal amylopectin digestion. WT mucosa was more sensitive to acarbose inhibition.