noun, plural: lactases
Lactases are secreted in the small intestine, kidneys, and liver of mammals. In humans, they are found mainly along the brush border membrane of the enterocytes that line the villi of the small intestine.1 LCT gene is the one that codes for lactases. Lactases digest lactose in milk and dairy products. Without this enzyme, the individual would not be able to digest lactose and as a result show symptoms of lactose intolerance. Thus, there are dairy products that add lactase in dairy products. Lactase is essential to digest lactose in humans to digest and break it down into D-galactose and D-glucose, which are absorbed through the intestinal walls and into the bloodstream.
1 Skovbjerg H, Sjöström H, Norén O (March 1981). "Purification and characterisation of amphiphilic lactase/phlorizin hydrolase from human small intestine".Eur. J. Biochem. 114 (3): 653–61.