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

Stable Identifier
Reaction [transition]
Homo sapiens
Digestion of lactose to yield glucose and galactose
Locations in the PathwayBrowser
SVG |   | PPTX  | SBGN
Click the image above or here to open this reaction in the Pathway Browser
The layout of this reaction may differ from that in the pathway view due to the constraints in pathway layout
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
Catalyst Activity

lactase activity of LCT dimer [plasma membrane]

Orthologous Events
Cite Us!