O-(N-acetyl-alpha-D-galactosaminyl)-L-serine residue
o-(n-acetyl-alpha-d-galactosaminyl)-l-serine residue
An <small>L</small>-α-amino acid residue derived from <em>O</em>-(<em>N</em>-acetyl-α-<small>D</small>-galactosaminyl)-<small>L</small>-serine.