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Debranching enzyme

 

 
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Debranching enzyme
 
 
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A debranching enzyme is a molecule that helps facilitate the breakdown of glycogen
Glycogen

Glycogen is a polysaccharide of glucose which functions as the secondary short term energy storage in animal cells. It is made primarily by the liver and the muscles, but can also be made by the brain and stomach....
.

anching enzymes are responsible for transferring three glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
 subunits of glycogen from one parallel chain to another. This shortens one linear branch while lengthening another. Afterwards, the donator branch will contain only one glucose residue
Residue (chemistry)

In chemistry, residue refers to the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group....
 with alpha-1,6 linkage. This remaining residue is in turn cut by alpha-1,6 glucosidase.






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A debranching enzyme is a molecule that helps facilitate the breakdown of glycogen
Glycogen

Glycogen is a polysaccharide of glucose which functions as the secondary short term energy storage in animal cells. It is made primarily by the liver and the muscles, but can also be made by the brain and stomach....
.

Function

Debranching enzymes are responsible for transferring three glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
 subunits of glycogen from one parallel chain to another. This shortens one linear branch while lengthening another. Afterwards, the donator branch will contain only one glucose residue
Residue (chemistry)

In chemistry, residue refers to the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group....
 with alpha-1,6 linkage. This remaining residue is in turn cut by alpha-1,6 glucosidase. This two step process is the general process by which the debranching enzymes "straighten out" glycogen into an unbranched glucose polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
.

These enzymes are important in glycogenolysis
Glycogenolysis

Glycogenolysis is the catabolism of glycogen by removal of a glucose monomer through cleavage with inorganic phosphate to produce glucose-1-phosphate....
 because the cutting enzyme, glycogen phosphorylase
Glycogen phosphorylase

Glycogen phosphorylase is one of the phosphorylase enzymes . Glycogen phosphorylase catalyzes the rate limiting step in the degradation of glycogen in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond....
, cannot cut a non-linear (or branched) glycogen chain.

Enzyme classification

The two debranching enzymes are:
  • 4-a-D-glucanotransferase - glucosyltransferase
  • amylo-a-1,6-glucosidase - glucosidase


Pathology

Deficiency in either of these enzymes will result in Glycogen storage disease type III
Glycogen storage disease type III

Glycogen storage disease type III is an autosomal recessive metabolic disorder and inborn error of metabolism, that is characterized by a deficiency in glycogen debranching enzymes....
.

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