polypeptide N-acetylgalactosaminyltransferase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: UDP-N-acetyl-D-galactosamine + polypeptide = UDP + N-acetyl-D-galactosaminyl-polypeptide. This reaction is the modification of serine or threonine residues in polypeptide chains by the transfer of a N-acetylgalactose from UDP-N-acetylgalactose to the hydroxyl group of the amino acid; it is the first step in O-glycan biosynthesis. [EC:2.4.1.41, ISBN:0879695595]

Polypeptide N-acetylgalactosaminyltransferase activity is a crucial enzymatic function involved in the biosynthesis of glycoproteins. This activity specifically catalyzes the transfer of N-acetylgalactosamine (GalNAc) from UDP-GalNAc to a polypeptide acceptor substrate. The reaction occurs at the hydroxyl group of serine or threonine residues within the polypeptide chain, initiating the formation of O-linked glycosylation. This process is essential for the synthesis of diverse glycoproteins, including mucins, immunoglobulins, and other proteins involved in cellular signaling, adhesion, and recognition. The enzyme responsible for this activity, known as polypeptide N-acetylgalactosaminyltransferase (ppGalNAcT), exhibits a wide range of substrate specificities and exhibits tissue-specific expression patterns. The precise amino acid sequence surrounding the glycosylation site significantly influences the efficiency of the transfer reaction, contributing to the diverse array of glycoproteins produced in various cellular contexts. The activity of ppGalNAcT is tightly regulated and can be influenced by factors such as cellular stress, developmental stage, and disease states.'
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Proteins (14)

Compounds (6)