Lactase

Lactase (or lactase-phloridzine hydrolase) is an intestinal digestive enzyme that catalyses the hydrolysis of lactose into glucose and galactose.

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.

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.