Lactase (or β-galactosidase) is the enzyme (EC 3.2.1.23) 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; most deficiency states are probably not due to defects in the lactase gene, but to mutations in the MCM6 gene.

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).

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

• E. coli β-galactosidase: PDB 1DPO