Difference Between N Glycosylation and O Glycosylation

Thekey differencebetween N glycosylation and O glycosylation isthat N glycosylation occurs in asparagine residues whereas O glycosylation occurs in the side chain of serine or threonine residues.

Glycosylation is the controlled enzymatic modification of an organic molecule such as a protein via the addition of asugar分子。这是一个重要的生化过程，也是细胞内二级蛋白质加工的高度调节机制。

CONTENTS

1.Overview and Key Difference
2.What is N Glycosylation
3.什么是糖基化
4.并排比较- N糖基化与O gcosylation in Tabular Form
5.概括

What is N Glycosylation?

N glycosylation or N-linked glycosylation is the attachment of an oligosaccharide sugar molecule to a nitrogen atom in the asparagine residue of a protein molecule. This sugar molecule is also named as glycan. It is attached to the nitrogen atom in theamidegroup of the asparagine residue. Further, this linking process is important in both the structure and function of some eukaryotic proteins. Moreover, this process takes place in eukaryotes, widely in archaea, and rarely in bacteria.

The attachment of a glycan residue to a protein requires the recognition of a consensus sequence. For example, N-linked glycans are almost always attached to the nitrogen atom of an asparagine side chain that occurs as a part of Asn-X-Ser/Thr consensus sequence. Here, X is any amino acid except proline (Pro). The N-linked glycans have both intrinsic and extrinsic functions.

There are important clinical applications of N glycosylation process. For example, it is associated with different diseases, including rheumatoid arthritis, type 1 diabetes, Crohn’s disease, and cancers. Moreover, many therapeutic proteins in the market are antibodies that are N-linked glycoproteins.

什么是糖基化？

O glycosylation or O-linked glycosylation is the attachment of a sugar molecule to the oxygen atom of serine or threonine residues in a protein molecule. This process is a post-transitional modification that happens after the synthesis of the protein. This process can take place in botheukaryotes and prokaryotes. E.g. in eukaryotes, N glycosylation occurs in the endoplasmic reticulum, Golgi apparatus and sometimes in the cytoplasm while in prokaryotes, it occurs in the cytoplasm.

During O glycosylation process, several sugars can be added to the serine or threonine, and this addition can affect the protein in different ways via changing the protein stability and by regulating the protein activity.

What is the Difference Between N Glycosylation and O Glycosylation?

N糖基化和O糖基化是重要的生化过程。n糖基化和O糖基化之间的主要区别在于，氮糖基化发生在天冬酰胺残基中，而O糖基化发生在丝氨酸或苏氨酸残基的侧链中。主要是，n糖基化发生在真核生物和古细菌中，而O糖基化仅发生在原核生物中。

Below is a summary tabulation of the difference between N glycosylation and O glycosylation.

概括– N Glycosylation vs O Glycosylation

In brief, N glycosylation or N-linked glycosylation is the attachment of an oligosaccharide sugar molecule to a nitrogen atom in the asparagine residue of a protein molecule. O glycosylation or O-linked glycosylation is the attachment of a sugar molecule to the oxygen atom of serine or threonine residues in a protein molecule. Therefore, the key difference between N glycosylation and O glycosylation is that N glycosylation occurs in asparagine residues, whereas O glycosylation occurs in the side chain of either serine or threonine residues.

Reference:

1. “Linked Glycosylation.” Science Direct.Available here.

Image Courtesy:

1. “Types of glycans” By Dna 621 – Own work(CC BY-SA 3.0)viaCommons Wikimedia
2. “Common O-glycans found on alpha-dystroglycan” By Waffeln – Own work(CC BY-SA 4.0)viaCommons Wikimedia