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LCT
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LAC LPH LPH1
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6530
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2
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q
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21
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32123
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603202
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3938
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NM_002299
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P09848
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(LCT), a member of the
β-galactosidase family of enzyme, is involved in the
Hydrolysis of
Lactose into constituent
Galactose and
Glucose Monomer s. In humans, lactase is present predominantly along the
Brush Border Membrane of the differentiated
Enterocyte s lining the
Villi of the
Small Intestine .
Lactase is essential for digestive hydrolysis of lactose in milk. Deficiency of the enzyme causes
Lactose Intolerance ; and most humans are normally lactose intolerant as adults.
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
Archaea 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.
Lactase persistence, the genetic trait in which intestinal lactase activity persists at childhood levels into adulthood, varies in frequency in different human populations, being most frequent in northern Europeans and certain African and Arabian nomadic tribes, who have a history of drinking fresh milk.
Lactase persistence is not due to mutations within the lactase gene, ''LCT'', but to mutations outside the gene in control regions that regulate its expression. They are two intronic variations (C/T and G/A) in the MCM6 gene, ''MCM6'', located approximately 14 kb (-13910) and 22 kb (-22018) upstream of ''LCT'', respectively Identification of a variant associated with adult-type hypolactasia ''Nat Genet. 2002 Feb; 30(2): 233-7''
Free text . C/T(-13910) variant has been shown that can function ''in vitro'' as a ''cis'' element capable of enhancing differential transcriptional activation of ''LCT'' promoter Lactase persistence DNA variant enhances lactase promoter activity in vitro: functional role as a cis regulatory element. ''Hum Mol Genet. 2003 Sep 15; 12(18): 2333-40.''
Free text .
Lactase produced commercially can be extracted both from from . 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.
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
