trimming of first mannose on A branch

Definition

Target type: biologicalprocess

The removal of the first alpha-1,2-linked mannose from the A-chain of a glycoprotein oligosaccharide in the endoplasmic reticulum. [GOC:bf, GOC:PARL, PMID:12829701]

The trimming of the first mannose on the A branch of N-linked glycans is a crucial step in the processing and quality control of glycoproteins. This process is carried out by the enzyme α-mannosidase I, which specifically removes the α1,6-linked mannose residue from the A branch of the Man9GlcNAc2 precursor oligosaccharide. This trimming event is essential for several reasons:

1. **Quality Control:** The removal of the α1,6-linked mannose is a critical step in the quality control of glycoprotein biosynthesis. If this mannose is not removed, the glycoprotein may be misfolded or unable to reach its proper cellular destination.

2. **Signal for Further Processing:** The trimming of the first mannose on the A branch signals to other enzymes that the glycoprotein is ready for further processing. This includes the removal of additional mannose residues by other α-mannosidases and the addition of other sugars by glycosyltransferases.

3. **Specificity for Different Pathways:** The specific trimming of the α1,6-linked mannose on the A branch allows for the creation of different types of N-glycans, which can have distinct functions. This trimming event is particularly important in the formation of complex N-glycans, which are involved in a wide range of cellular processes.

The trimming of the first mannose on the A branch occurs in the lumen of the endoplasmic reticulum (ER), where N-linked glycans are initially assembled. This process requires the presence of calcium ions and is sensitive to certain inhibitors. This trimming event is also influenced by the specific glycoprotein being processed, as different proteins may have different N-glycan processing requirements.

In summary, the trimming of the first mannose on the A branch of N-linked glycans is a critical step in glycoprotein processing that ensures proper folding, quality control, and the creation of diverse N-glycans. This process is essential for the proper function of many glycoproteins and plays a vital role in a wide range of cellular processes.'
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Proteins (1)

Compounds (1)