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Literature summary for 3.2.1.10 extracted from
- Structure-function analysis of human sucrase-isomaltase identifies key residues required for catalytic activity (2017), J. Biol. Chem., 292, 11070-11078 .
Cloned(Commentary)
| Cloned (Comment) | Organism |
|---|---|
| gene SI, sequence comparisons, recominant expression of wild-type and mutant enzymes in COS-1 cells | Homo sapiens |
Protein Variants
| Protein Variants | Comment | Organism |
|---|---|---|
| D1394E | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D1500E | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D1500N | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D1500S | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D1500Y | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D505E | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D604E | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D604N | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D604S | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| D604Y | site-directed mutagenesis of a catalytic residue, the mutant shows reduced maltase activity compared to wild-type | Homo sapiens |
| additional information | mutagenesis of the proton donor residues and the nucleophilic catalyst residues in each SI subunit of the enzyme. All of the mutants reveal expression levels and maturation rates comparable with those of the wild-type species and the corresponding nonmutated subunits are functionally active. Inactivation of one subunit of SI by mutagenesis is not paralleled by loss or reduction in the functional capacity of the other | Homo sapiens |
Inhibitors
| Inhibitors | Comment | Organism | Structure |
|---|---|---|---|
| D-glucose | 22% inhibition at 0.7 mM, glucose product inhibition regulates the activities of both enzyme SI subunits | Homo sapiens |  |
KM Value [mM]
| KM Value [mM] | KM Value Maximum [mM] | Substrate | Comment | Organism | Structure |
|---|---|---|---|---|---|
| additional information | - |
additional information | Michaelis-Menten kinetics | Homo sapiens | |
| 8.9 | - |
isomaltose | recombinant wild-type enzyme, pH 6.2, 37°C | Homo sapiens | |
| 9.8 | - |
isomaltose | recombinant wild-type enzyme, pH 6.2, 37°C, in presence of 0.7 mM glucose | Homo sapiens | |
Localization
| Localization | Comment | Organism | GeneOntology No. | Textmining |
|---|---|---|---|---|
| brush border membrane | - |
Homo sapiens | 31526 | - |
| membrane | membrane-associated | Homo sapiens | 16020 | - |
Natural Substrates/ Products (Substrates)
| Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| isomaltose + H2O | Homo sapiens | - |
2 D-glucose | - |
? | |
Organism
| Organism | UniProt | Comment | Textmining |
|---|---|---|---|
| Homo sapiens | P14410 | - |
- |
Source Tissue
| Source Tissue | Comment | Organism | Textmining |
|---|---|---|---|
| small intestine | - |
Homo sapiens | - |
Substrates and Products (Substrate)
| Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| isomaltose + H2O | - |
Homo sapiens | 2 D-glucose | - |
? | |
| additional information | the enzyme performs hydrolysis of sucrose and maltose by an alpha-D-glucosidase-type action (EC 3.2.1.48), and hydrolysis of (1->6)-alpha-D-glucosidic linkages in some oligosaccharides produced from starch and glycogen by alpha-amylase, and in isomaltose (EC 3.2.1.10), reaction mechanism | Homo sapiens | ? | - |
? | |
Synonyms
| Synonyms | Comment | Organism |
|---|---|---|
| sucrase-isomaltase | - |
Homo sapiens |
Temperature Optimum [°C]
| Temperature Optimum [°C] | Temperature Optimum Maximum [°C] | Comment | Organism |
|---|---|---|---|
| 37 | - |
assay at | Homo sapiens |
pH Optimum
| pH Optimum Minimum | pH Optimum Maximum | Comment | Organism |
|---|---|---|---|
| 6.2 | - |
assay at | Homo sapiens |
General Information
| General Information | Comment | Organism |
|---|---|---|
| evolution | the enzyme belongs to the glycoside hydrolase family 31 (GH31). All GH31 enzymes share a consensus sequence harboring an aspartic acid residue as a catalytic nucleophile | Homo sapiens |
| malfunction | reduced or absent enzymatic levels of sucrase-isomaltase (SI) can lead to carbohydrate malabsorption with gastrointestinal symptoms, such as osmotic diarrhea, bloating, flatulence, and vomiting. SI deficiencies can occur primarily as a consequence of mutations in the coding region of the SI gene, referred to as congenital sucrase-isomaltase deficiency (CSID). Deleterious mutations are associated with alterations in the intracellular trafficking, functional deficits, and missorting of SI. Secondary SI deficiencies, on the other hand, arise collaterally to other organ pathologies in the intestine, in which the integrity and/or the normal physiology of the intestinal epithelium is severely affected, for example in intestinal ulcers or infections and inflammatory bowel disease. Inactivation of one subunit of SI by mutagenesis is not paralleled by loss or reduction in the functional capacity of the other | Homo sapiens |
| metabolism | sucrase-isomaltase (SI) catalyzes the final step of carbohydrate digestion by breaking disaccharides and oligosaccharides to absorbable monosaccharides | Homo sapiens |
| additional information | enzyme structure-function analysis, overview | Homo sapiens |
| physiological function | sucrase-isomaltase (SI, EC 3.2.1.48 and 3.2.1.10) is an intestinal membrane-associated alpha-glucosidase that breaks down di- and oligosaccharides to absorbable monosaccharides. The enzyme has two homologous functional subunits (sucrase and isomaltase) that both belong to the glycoside hydrolase family 31 (GH31) and differ in substrate specificity. Glucose product inhibition regulates the activities of both SI subunits | Homo sapiens |
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