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Effect of Mouse Maltase‐glucoamylase (Mgam) Knockout on Starch Digestion to Glucose
Author(s) -
Nichols Buford L,
RobayoTorres Claudia C,
Ao Zihua,
Hamaker Bruce R,
Brayer Gary D,
Sterchi Erwin E,
QuezadaCalvillo Roberto
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a177-c
Subject(s) - chemistry , acarbose , amylopectin , maltose , dextrin , digestion (alchemy) , maltotriose , maltase , starch , amylase , biochemistry , enzyme , food science , amylose , chromatography
Digestion of starch requires activities provided by six different α‐glucosidase enzymes. Two activities are luminal α‐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. α‐Glucogenesis from MDx substrate was 20 X faster in WT. α‐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 α‐glucogenesis by 20 X. α‐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.