Lactase
From Wikipedia, the free encyclopedia.
Lactase is a member of the β-galactosidase family of enzyme: enzymes that cleave off β-oxygen bonded attachments to galactose. Lactase (EC 3.2.1.23) is involved in the hydrolysis of lactose to galactose and glucose. In humans, it is produced in the digestive tract. Deficiency of the enzyme causes lactose intolerance; and most humans are normally lactose intolerant as adults. Persistant lactase production as adults in humans is probably not due to mutations in the lactase gene, but to mutations in the MCM6 gene that may control lactase productions rates.
Characteristics
Lactase has an optimum temperature of about 48 °C for its activity and an optimum pH of 6.5. In humans, the gene is localised on the second chromosome (2q21). Bacterial and Archea lactase lack a membrane binding domain and free float around the cell, these also tend to be more general β-galactosidase that will cleave more then just lactose.
Industrial use
Lactase produced commercially can be extracted from yeast fungi such as Kluyveromyces fragilis. 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.
External links
Also used to screen for blue white colonies into the MCS of various plasmid vectors in E.Coli or other bacteria, as the lacZ gene is destroyed
