Structure-function analysis of human sucrase-isomaltase identifies key residues required for catalytic activity.

The Journal of Biological Chemistry
Birthe GerickeHassan Y Naim

Abstract

Sucrase-isomaltase (SI) is an intestinal membrane-associated α-glucosidase that breaks down di- and oligosaccharides to absorbable monosaccharides. SI has two homologous functional subunits (sucrase and isomaltase) that both belong to the glycoside hydrolase family 31 (GH31) and differ in substrate specificity. All GH31 enzymes share a consensus sequence harboring an aspartic acid residue as a catalytic nucleophile. Moreover, crystallographic structural analysis of isomaltase predicts that another aspartic acid residue functions as a proton donor in hydrolysis. Here, we mutagenized the predicted proton donor residues and the nucleophilic catalyst residues in each SI subunit. We expressed these SI variants in COS-1 cells and analyzed their structural, transport, and functional characteristics. All of the mutants revealed expression levels and maturation rates comparable with those of the wild-type species and the corresponding nonmutated subunits were functionally active. Thereby we determined rate and substrate specificity for each single subunit without influence from the other subunit. This approach provides a model for functional analysis of the single subunits within a multidomain protein, achieved without the necessity to ...Continue Reading

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Citations

Aug 16, 2018·Organic & Biomolecular Chemistry·Ida M B KnudsenHenrik H Jensen
Jun 12, 2019·International Journal of Molecular Sciences·Adrián Hernández-DíazcouderFausto Sánchez-Muñoz
Sep 27, 2018·International Journal of Molecular Sciences·Marcela González-MontoyaCristina Martínez-Villaluenga
Aug 23, 2020·Cells·Sepideh Fallah, Jean-François Beaulieu
Mar 17, 2020·International Journal of Biological Macromolecules·Shaik AbduldileepRam Rajasekharan
Apr 6, 2021·Environmental Science. Nano·Alba García-RodríguezGretchen J Mahler

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