4-Nitrophenyl-N-acetyl-α-D-galactosaminide
4-Nitrophenyl-N-acetyl-α-D-galactosaminide (pNP-GalNAc) can be used as a chromogenic substrate for N-acetyl-D-galactosaminase. 4-Nitrophenyl-N-acetyl-α-D-galactosaminide is cleaved by N-acetyl-D-galactosaminase to generate a yellow solution. The enzyme activity is quantitatively determined by absorbance detection.