sucrase-isomaltase; invertase; beta-fructofuranosidase; limit dextrinase; palatinase (SI)

Function: - role in the final stage of carbohydrate digestion - hydrolysis of (1->6)-alpha-D-glucosidic linkages in some oligosaccharides produced from starch & glycogen by alpha-amylase, & in isomaltose Structure: - sulfated (putative) - belongs to the glycosyl hydrolase 31 family contains 1 P-type (trefoil) domain - sucrase & isomaltase subunits stay associated with one another in a complex by non-covalent linkages - precursor is proteolytically cleaved when exposed to pancreatic proteases in the intestinal lumen - hydrolysis of sucrose & maltose by an alpha- D-glucosidase-type action Compartment: - apical cell membrane - brush border Expression: - expressed in the poorly differentiated crypt cells of the small intestine as well as in the mature villous cells - expressed at very low levels in the colon Pathology: - defects in SI are the cause of congenital sucrase-isomaltase deficiency Genetics: - there is a high degree of homology between the isomaltase & sucrase portions (41% of amino acid identity) indicating that this protein is evolved by partial gene duplication

General

glycoprotein glycosidase (glycoside hydrolase) membrane protein

Properties

SIZE: entity length = 1827 aa MW = 209 kD COMPARTMENT: cellular membrane MOTIF: transmembrane domain {13-32} threonine-rich region {43-60} MOTIF: threonine residue (SEVERAL) P-type {62-109} MOTIF: cysteine residue {C63} MODIFICATION: cysteine residue {C94} cysteine residue {C77} MODIFICATION: cysteine residue {C93} cysteine residue {C88} MODIFICATION: cysteine residue {C106} cysteine residue {C93} MODIFICATION: cysteine residue {C77} cysteine residue {C94} MODIFICATION: cysteine residue {C63} N-glycosylation site {N99} cysteine residue {C106} MODIFICATION: cysteine residue {C88} Isomaltase {110-1007} MOTIF: N-glycosylation site {N437} N-glycosylation site {N455} aspartate residue {D505} glutamate residue {E508} N-glycosylation site {N823} N-glycosylation site {N855} N-glycosylation site {N904} N-glycosylation site {N926} Sucrase {1008-1827} MOTIF: N-glycosylation site {N1235} N-glycosylation site {N1303} N-glycosylation site {N1340} N-glycosylation site {N1354} aspartate residue {D1394} glutamate residue {E1397} N-glycosylation site {N1403} aspartate residue {D1500} N-glycosylation site {N1535} N-glycosylation site {N1572} N-glycosylation site {N1675} N-glycosylation site {N1748} N-glycosylation site {N1763} N-glycosylation site {N1815}

Database Correlations

OMIM correlations MORBIDMAP 609845 UniProt P14410 PFAM correlations Entrez Gene 6476 Kegg hsa:6476 ENZYME 3.2.1.10

References

UniProt :accession P14410