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Lactase
 
 
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Lactase (LCT), a part of the ß-galactosidase family of enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s, is a glycoside hydrolase
Glycoside hydrolase

Glycoside hydrolases catalysis the hydrolysis of the glycosidic linkage to generate two smaller sugars. They are extremely common enzymes with roles in nature including degradation of biomass such as cellulose and hemicellulose, in anti-bacterial defense strategies , in pathogenesis mechanisms and in normal cellular function ....
 involved in the hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
 of the disaccharide
Disaccharide

A disaccharide is a sugar composed of two monosaccharides.'Disaccharide' is one of the four chemical groupings of carbohydrates ....
 lactose
Lactose

Lactose is a sugar that is found most notably in milk. Lactose makes up around 2?8% of milk . The name comes from the Latin word for milk, plus the -ose ending used to name sugars....
 into constituent galactose
Galactose

Galactose is a type of Carbohydrate which is less sweetness than glucose. It is considered a nutritive sweetener because it has food energy.Galactan is a polymer of the sugar galactose....
 and glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
 monomer
Monomer

A monomer is a small molecule that may become Chemistry chemical bonding to other monomers to form a polymer....
s. In humans, lactase is present predominantly along the brush border
Brush border

A brush border is the name for the microvilli-covered surface of simple cuboidal epithelium and simple columnar epithelium cells found in certain locations of the body....
 membrane
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
 of the differentiated enterocyte
Enterocyte

Enterocytes, or intestinal absorptive cells, are simple columnar epithelial cells found in the small intestines and colon. A glycocalyx surface coat contains digestive enzymes....
s lining the villi of the small intestine
Small intestine

In vertebrates, including mammals, reptiles, birds, and bony fish, the small intestine is the part of the gastrointestinal tract following the stomach, and is where the vast majority of digestion takes place....
.

Lactase is essential for digestive hydrolysis of lactose in milk. Deficiency of the enzyme causes lactose intolerance
Lactose intolerance

Lactose intolerance is the inability to Metabolism lactose, a sugar found in milk and other dairy products, because the required enzyme lactase is absent in the intestinal system or its availability is lowered....
.

The optimum temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 for lactase is about 48 °C (118.4 °F) for its activity and has an optimum pH
PH

pH is a measure of the Acid or Base of a solution. It is defined as the cologarithm of the Activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations....
 of 6.5.

ase produced commercially can be extracted both from yeast
Yeast

Yeasts are eukaryote microorganisms classified in the Kingdom fungus, with about 1,500 species currently described; they dominate fungal diversity in the oceans....
s such as Kluyveromyces fragilis and Kluyveromyces lactis
Kluyveromyces lactis

Kluyveromyces lactis is a Kluyveromyces yeast commonly used for Genetics studies and industrial applications. Its name comes from the ability to assimilate lactose and convert it into lactic acid....
 and from fungi
Fungus

A fungus is a Eukaryote organism that is a member of the Kingdom Fungi . The fungi are a monophyletic group, also called the Eumycota , that is phylogeny distinct from the morphologically similar slime molds and water molds ....
, such as Aspergillus niger
Aspergillus niger

Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food....
 and Aspergillus oryzae
Aspergillus oryzae

Aspergillus oryzae is a hypha fungus used in Chinese cuisine and Japanese cuisine which fermentation soybeans to produce soy sauce and miso....
.






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Lactase (LCT), a part of the ß-galactosidase family of enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s, is a glycoside hydrolase
Glycoside hydrolase

Glycoside hydrolases catalysis the hydrolysis of the glycosidic linkage to generate two smaller sugars. They are extremely common enzymes with roles in nature including degradation of biomass such as cellulose and hemicellulose, in anti-bacterial defense strategies , in pathogenesis mechanisms and in normal cellular function ....
 involved in the hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
 of the disaccharide
Disaccharide

A disaccharide is a sugar composed of two monosaccharides.'Disaccharide' is one of the four chemical groupings of carbohydrates ....
 lactose
Lactose

Lactose is a sugar that is found most notably in milk. Lactose makes up around 2?8% of milk . The name comes from the Latin word for milk, plus the -ose ending used to name sugars....
 into constituent galactose
Galactose

Galactose is a type of Carbohydrate which is less sweetness than glucose. It is considered a nutritive sweetener because it has food energy.Galactan is a polymer of the sugar galactose....
 and glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
 monomer
Monomer

A monomer is a small molecule that may become Chemistry chemical bonding to other monomers to form a polymer....
s. In humans, lactase is present predominantly along the brush border
Brush border

A brush border is the name for the microvilli-covered surface of simple cuboidal epithelium and simple columnar epithelium cells found in certain locations of the body....
 membrane
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
 of the differentiated enterocyte
Enterocyte

Enterocytes, or intestinal absorptive cells, are simple columnar epithelial cells found in the small intestines and colon. A glycocalyx surface coat contains digestive enzymes....
s lining the villi of the small intestine
Small intestine

In vertebrates, including mammals, reptiles, birds, and bony fish, the small intestine is the part of the gastrointestinal tract following the stomach, and is where the vast majority of digestion takes place....
.

Lactase is essential for digestive hydrolysis of lactose in milk. Deficiency of the enzyme causes lactose intolerance
Lactose intolerance

Lactose intolerance is the inability to Metabolism lactose, a sugar found in milk and other dairy products, because the required enzyme lactase is absent in the intestinal system or its availability is lowered....
.

The optimum temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 for lactase is about 48 °C (118.4 °F) for its activity and has an optimum pH
PH

pH is a measure of the Acid or Base of a solution. It is defined as the cologarithm of the Activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations....
 of 6.5.

Industrial use

Lactase produced commercially can be extracted both from yeast
Yeast

Yeasts are eukaryote microorganisms classified in the Kingdom fungus, with about 1,500 species currently described; they dominate fungal diversity in the oceans....
s such as Kluyveromyces fragilis and Kluyveromyces lactis
Kluyveromyces lactis

Kluyveromyces lactis is a Kluyveromyces yeast commonly used for Genetics studies and industrial applications. Its name comes from the ability to assimilate lactose and convert it into lactic acid....
 and from fungi
Fungus

A fungus is a Eukaryote organism that is a member of the Kingdom Fungi . The fungi are a monophyletic group, also called the Eumycota , that is phylogeny distinct from the morphologically similar slime molds and water molds ....
, such as Aspergillus niger
Aspergillus niger

Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food....
 and Aspergillus oryzae
Aspergillus oryzae

Aspergillus oryzae is a hypha fungus used in Chinese cuisine and Japanese cuisine which fermentation soybeans to produce soy sauce and miso....
. Its primary commercial use is to break down lactose in milk to make it suitable for people with lactose intolerance
Lactose intolerance

Lactose intolerance is the inability to Metabolism lactose, a sugar found in milk and other dairy products, because the required enzyme lactase is absent in the intestinal system or its availability is lowered....
. However, the U.S. Food and Drug Administration (FDA) has not formally evaluated the effectiveness of these products. Lactase is also used in the manufacture of ice cream
Ice cream

Ice cream or ice-cream is a frozen dessert usually made from dairy products, such as milk and cream, combined with fruits or other ingredients....
. 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
Whey

Whey or milk plasma is the liquid remaining after milk has been curdled and strained; it is a by-product of the manufacture of cheese or casein and has several commercial uses....
 into syrup.

Lactase is also used to screen for blue white colonies into the MCS of various plasmid vectors in Escherichia coli
Escherichia coli

'Escherichia coli' , is a Gram negative bacterium that is commonly found in the lower gastrointestinal tract of warm-blooded animals. Most E....
 or other bacteria.

The reaction that lactase catalyzes is C12H22011 + H20 --> C6H1206 + C6H1206 + heat.

External links

  • E. coli ß-galactosidase: