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What is a glycosidic bond?

Glycosidic bond

In many of the food consumed daily in table sugar, in the trunks of trees and even in some animals such as lobsters, you may find links glucoside . This type of link is of vital importance for many substances, basically it could be said that life could not exist without them since they are even part of the DNA of the human body.

What is glycosidic bond, characteristics, formation, types, properties 

What is a glycosidic bond?

glycosidic bond is a covalent chemical bond that is responsible for holding glycosides together , which can hold carbohydrates together with other types of functional groups or molecules.

  • Characteristics of a glycosidic bond
  • How a glycosidic bond is formed
  • Types
  • Properties of the glycosidic bond
  • Nomenclature
  • How to differentiate an alpha and beta glycosidic bond
  • Examples

Characteristics of a glycosidic bond

Glycosidic bonds are covalent , in other words, they are a union that occurs between atoms through a sharing of the pairs of electrons they contain. It is important to mention that these types of bonds are present in different cellular contexts , for example the union of sphingolipids , which are essential components in the cell membranes of different types of organisms. Its main characteristics are mentioned below:

  • They are links that occur between sugars and other types of molecules .
  • They are considered essential links for life.
  • The formation of polysaccharides will depend on them .
  • It has three-dimensional structures that are very different from each other.
  • They perform different types of biological activities .
  • Such a bond is the most flexible part of an oligo- moiety.
  • They can be hydrolyzed very easily, especially in those environments that are acidic.
  • They are very resistant to alkaline environments.
  • They can be hydrolyzed by means of glycosidase enzymes .
  • They can be formed from the union of a sugar with any other type of compound that is hydroxylated.
  • They are necessary for the glycosylation of proteins , a process that occurs within the endoplasmic reticulum and in the Golgi complex , an activity of great importance for proteins.

How a glycosidic bond is formed

This type of bond is formed when two molecules that belong to monosaccharides join through the anomeric carbon that one of them has. The formation occurs through condensation and its reactions in which a water molecule can be released for each of the bonds that are formed. These different reactions that form glycosidic bonds are also catalyzed by enzymes.

Types

There are four types of glycosidic bonds that can be differentiated, these are:

Glycosidic bonds between monosaccharides

This type of bond corresponds to oligo- and polysaccharides. This bond depends on the nature of the sugars and the amount of carbon atoms that are present.

Glycosidic bonds between glycoproteins

This refers to the bonds that occur between proteins or lipids that also include carbohydrates.

S-glucosidic bonds

These are bonds that occur between proteins and carbohydrates.

C-glucosidic bonds

They were observed as a type of post-translational modification and were present in human urine.

In nature you can find types of glycosidic bonds known as sucrose , maltose , isomalt , gentiobiose and lactose .

Properties of the glycosidic bond

Among the main properties it can be mentioned that the N-glucosidic bond is formed as a result of the union of an -OH and an amino compound to result in the formation of amino sugars . For its part, the O-glucosidic bond occurs between two -OH that belong to two monosaccharides where the condensation of the water molecule reacts to the anomeric carbon.

It is also important to mention that glycosidic bonds have an analogous relationship with oligosaccharides. This type of bond is considered as the region with the greatest flexibility in a polysaccharide portion because its structure is rigid.

Nomenclature

The glycosidic bond can have three different types of nomenclatures. The first of them is changing the “o” by the cyclic form of the monosaccharide for ” gone “ and, in addition, the name of the R group must be placed as a different word before “gone” . The word ” glycosyloxy ” can also be used and is placed in front of the monosaccharide. Lastly, the term O-glycosyl, N-glycosyl, S-glycosyl or C-glycosyl can be used as a prefix.

How to differentiate an alpha and beta glycosidic bond

In order to differentiate them, it is important to remember that in the glucose molecule there is a type of glycosidic union to which different names are given related to the structure and the direction in which it is located, in addition to taking into account the site where it is located. the OH . An alpha or beta bond can be up or down, in other words, when the OH is in a low position, then it is an alpha bond, and conversely if it is up it will be a beta bond .

Examples

It should be remembered that this type of bond is formed when monosaccharides , in other words, simple sugars, join together and thus give rise to larger molecules. When the bonds form more than ten molecules, they are called oligosaccharides and as examples we can mention chitin , glycogen , starch , cellulose and gelose .

When the bonds are formed by two simple sugars then they are known by the name of disaccharides and this type is the most common form because it is found in many types of food such as galactose , sucrose , maltose , lactose , isomalt , lactulose and turanose .

Some more specific examples are mentioned below:

Glycosidic bond of sucrose

It is formed through a dicarbonyl bond of glucose and fructose. The latter rotates to face its carbon 2 with carbon 1 that contains glucose.

Lactose glycosidic bond

It is formed through a monocarbonyl bond of galactose and glucose and is also a reducing bond.

Glycosidic bond of maltose

It is formed by a monocarbonyl type bond between glucoses, it is easily hydrolyzed and in it, the glucose is free.

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