Structure of lactase
Lactase is a protein formed from 1,927 amino acids and has two functional domains: a lactase domain and a phloridzine hydrolase domain. It has active nucleophilic and proton doner sites and contains a modified amino acid, a phosphotyrosine, in its protein chain .
Lactase is synthesised by intestinal cells and excreted into the lumen of the gastrointestinal tract.
Function of lactase
The lactase family belongs to the hydrolase family and has two enzyme activities:
- firstly, a phloridzin hydrolase activity which hydrolyses phloridzine into phloretin and glucose, and secondly
- a lactase activity which hydrolyses lactose, a complex sugar into glucose and galactose, simple sugars which can be assimilated by the body.
Lactase is an intestinal digestive enzyme © Catherine Germain, Wikimedia, GFDL 1.2