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Maturation of sucrase-isomaltase complex in human fetal small and large intestine during gestation
Insights
The human sucrase-isomaltase enzyme complex appears in the small intestine during gestation and the large intestine later. Fetal forms differ from adult forms, with distinct molecular weights and migration patterns.
Area of Science:
- Biochemistry
- Human Physiology
- Developmental Biology
Background:
- Sucrase-isomaltase is a key enzyme in carbohydrate digestion.
- Its expression and molecular form during human development are not fully understood.
Purpose of the Study:
- To investigate the expression and molecular characteristics of the sucrase-isomaltase complex in the human fetal intestine.
- To compare fetal and adult forms of the enzyme.
Main Methods:
- Brush-border membrane fractions were isolated from human fetal intestines.
- Immunoblotting and SDS-PAGE were used to analyze the molecular forms of sucrase-isomaltase.
Main Results:
- Sucrase-isomaltase is expressed in the small intestine throughout gestation and in the large intestine from 12-30 weeks.
- Before 30 weeks, only the high molecular weight prosucrase-isomaltase form is present; thereafter, two subunits also appear.
- Fetal sucrase-isomaltase (proform and subunits) exhibits faster gel electrophoresis mobility than the adult form, a difference enhanced by sialic acid removal.
- Fetal enzymes from the colon and small intestine are identical.
Conclusions:
- The molecular form of human sucrase-isomaltase undergoes significant changes during fetal development.
- These developmental changes in enzyme structure may have implications for intestinal function.
- The identical nature of fetal colonic and small intestinal enzymes suggests a common developmental origin or regulation.
Abstract:
Sucrase-isomaltase complex is expressed in human small intestine throughout gestation and in the large intestine between 12 and 30 wk. The molecular form of the enzyme was studied in the brush-border membrane fractions by the immunoblotting method. Before 30 wk of gestation, the enzyme is present only as the high molecular weight prosucrase-isomaltase, while from 30 wk until birth the two subunits are also present. The fetal enzyme, as its proform and as its two subunits, has a faster mobility in sodium-dodecylsulfate polyacrylamide gel electrophoresis, than the adult enzyme (removal of sialic acid residues from fetal enzymes emphasizes this difference). The colonic and the small intestinal fetal enzymes are identical.