label: L-seryl-[protein] + UDP-N-acetyl-alpha-D-galactosamine => 3-O-[N-acetyl-alpha-D-galactosaminyl]-L-seryl-[protein] + UDP + H(+)
label_lc: l-seryl-[protein] + udp-n-acetyl-alpha-d-galactosamine => 3-o-[n-acetyl-alpha-d-galactosaminyl]-l-seryl-[protein] + udp + h(+)