polypeptide N-acetylgalactosaminyltransferase-like protein 5; protein-UDP acetylgalactosaminyltransferase 15; UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 15; polypeptide GalNAc transferase 15; GalNAc-T15; pp-GaNTase 15 (GALNTL5, GALNT15)

Function

• glycosylation (putative, see structure below)
• 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

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

Cofactors: 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
• In contrast to other members of the family, it lacks the C-terminal ricin B-type lectin domain, which contributes to the glycopeptide specificity, thus function is certain
• belongs to the glycosyltransferase 2 family, GalNAc-T subfamily

Compartment

• Golgi membrane

Alternative splicing

• named isoforms=2

More general terms

• polypeptide N-acetylgalactosaminyltransferase

Database

• UniProt: http://www.uniprot.org/uniprot/Q7Z4T8.html