Reactome | lactose + H2O => D-glucose + D-galactose

lactose + H2O => D-glucose + D-galactose

Stable Identifier

R-HSA-189062

Type

Reaction [transition]

Species

Homo sapiens

Compartment

extracellular region, plasma membrane

Synonyms

Digestion of lactose to yield glucose and galactose

ReviewStatus

5/5

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lactose + H2O => D-glucose + D-galactose

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Extracellular lactose is hydrolyzed to yield molecules of glucose and galactose, in a reaction catalyzed by the lactase activity of lactase-phlorizin hydrolase associated with the plasma membrane. In the body, lactase-phlorzin hydrolase is found on the external face of enterocytes in microvilli of the small intestine (Hauri et al. 1985). Expression of the enzyme is developmentally regulated and subject to a genetic polymorphism: enzyme levels fall after weaning but the extent of the fall varies sharply between human populations (Grand et al. 2003; Swallow 2003). The lactase-phlorizin hydrolase polypeptide undergoes dimerization and two rounds of proteolytic cleavage in the course of its maturation and transport to the cell surface (Grunberg and Sterchi 1995; Wuthrich et al. 1996; Behrendt et al. 2010).

Literature References

PubMed ID	Title	Journal	Year
14616060	Genetics of lactase persistence and lactose intolerance Swallow, DM	Annu Rev Genet	2003
7487100	Human lactase-phlorizin hydrolase: evidence of dimerization in the endoplasmic reticulum Sterchi, EE, Grunberg, J	Arch Biochem Biophys	1995
8951031	Proteolytic processing of human lactase-phlorizin hydrolase is a two-step event: identification of the cleavage sites Jacob, R, Wuthrich, M, Radebach, I, Sterchi, EE, Hahn, D, Grunberg, J, Naim, HY	Arch Biochem Biophys	1996
3897250	Expression and intracellular transport of microvillus membrane hydrolases in human intestinal epithelial cells Hauri, HP, Fransen, JA, Bienz, D, Marxer, A, Sterchi, EE	J Cell Biol	1985
12692040	Changing genes; losing lactase Montgomery, RK, Hirschhorn, JN, Grand, RJ, Chitkara, DK	Gut	2003
19955176	Structural hierarchy of regulatory elements in the folding and transport of an intestinal multidomain protein Polaina, J, Behrendt, M, Naim, HY	J. Biol. Chem.	2010