AskDefine | Define lactase

Dictionary Definition

lactase n : any of a group of enzymes (trade name Lactaid) that hydrolyze lactose to glucose and galactose [syn: Lactaid]

User Contributed Dictionary



  1. A β-galactosidase enzyme that is involved in the hydrolysis of the disaccharide lactose into constituent galactose and glucose monomers.



es-verb-form lactar

Extensive Definition

Lactase (LCT), a member of the β-galactosidase family of enzymes, is a glycoside hydrolase involved in the hydrolysis of the disaccharide lactose into constituent galactose and glucose monomers. In humans, lactase is present predominantly along the brush border membrane of the differentiated enterocytes lining the villi of the small intestine.
Lactase is essential for digestive hydrolysis of lactose in milk. Deficiency of the enzyme causes lactose intolerance.
The optimum temperature for lactase is about 48 °C (118.4 °F) for its activity and has an optimum pH of 6.5.

Industrial use

Lactase produced commercially can be extracted both from yeasts such as Kluyveromyces fragilis and Kluyveromyces lactis and from fungi, such as Aspergillus niger and Aspergillus oryzae. Its primary commercial use is to break down lactose in milk to make it suitable for people with lactose intolerance. Lactase is also used in the manufacture of ice cream. Because glucose and galactose are sweeter than lactose, lactase produces a more pleasant taste. Lactose also crystallises at the low temperatures of ice cream; however, its constituent products stay liquid and contribute to a smoother texture. Lactase is used in the conversion of whey into syrup.
Lactase is also used to screen for blue white colonies into the MCS of various plasmid vectors in Escherichia coli or other bacteria.


lactase in Danish: Laktase
lactase in German: Lactase
lactase in Spanish: Lactasa
lactase in Esperanto: Laktazo
lactase in French: Lactase
lactase in Icelandic: Laktasi
lactase in Italian: Lattasi
lactase in Hebrew: לקטאז
lactase in Dutch: Lactase
lactase in Japanese: ラクターゼ
lactase in Occitan (post 1500): Lactasa
lactase in Polish: Laktaza
lactase in Portuguese: Lactase
lactase in Finnish: Laktaasi
lactase in Swedish: Laktas
lactase in Ukrainian: Лактаза
lactase in Chinese: 乳糖酶
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