lactase phlorizin hydrolase; lactase glycosylceramidase; lactase (LCT, LPH)

Function

• LCT splits lactose in the small intestine

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

Glycosyl-N-acylsphingosine + H2O
          <-->
N-acylsphingosine + a sugar

Structure

• exhibits 4 regions (I-IV) of internal homology; thus LPH might have evolved by two cycles of partial gene duplication
• belongs to the glycosyl hydrolase 1 family

Compartment

• apical cell membrane
• brush border

Expression

• intestine
• developmental down-regulation of lactase activity during childhood or early adulthood
• down-regulation of lactase activity operates at the transcriptional level & it is associated with a noncoding variation in the MCM6 gene, located in the upstream vicinity of LCT

Pathology

• defects in LCT are the cause of congenital lactase deficiency
• developmental down-regulation of lactase activity during childhood or early adulthood results in lactose intolerance

Pharmacology

• oral formulation used in treatment of lactase deficiency

More general terms

• glucosidase
• membrane protein
• metabolic agent (metabolic modifier)

Additional terms

• lactase

Database

• UniProt: http://www.uniprot.org/uniprot/P09848.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=3938
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:3938
• OMIM: https://mirror.omim.org/entry/223000
• OMIM: https://mirror.omim.org/entry/223100
• OMIM: https://mirror.omim.org/entry/603202