polypeptide N-acetylgalactosaminyltransferase 5 (protein-UDP acetylgalactosaminyltransferase 5, UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 5, polypeptide GalNAc transferase 5, GalNAc-T5, pp-GaNTase 5, GALNT5)

Function

• glycosylation
• catalyzes the initial reaction in O-linked oligosaccharide biosynthesis, transfer of an N-acetyl-D-galactosamine residue to a Ser or Thr on the protein
• activity toward EA2 peptide, but weak activity toward Muc2 or Muc1b
• interacts with EXT2
• does not interact with EXT1, EXTL1 or EXTL3

UDP-N-acetyl-D-galactosamine + polypeptide
                   <-->
UDP + N-acetyl-D-galactosaminyl-polypeptide

Cofactor: Mn+2, Ca+2

Structure

• 2 conserved domains in the glycosyltransferase region
  • N-terminal domain (domain A, also called GT1 motif), involved in Mn+2 coordination & substrate binding
  • C-terminal domain (domain B, also called Gal/GalNAc-T motif) involved in catalysis & UDP-Gal binding
• ricin B-type lectin domain binds to GalNAc & contributes to glycopeptide specificity
• belongs to the glycosyltransferase 2 family, GalNAc-T subfamily.
• contains 1 ricin B-type lectin domain

Compartment

Golgi membrane

More general terms

• polypeptide N-acetylgalactosaminyltransferase

Database

• UniProt: http://www.uniprot.org/uniprot/Q7Z7M9.html