4-Nitrophenyl α-D-galactopyranoside
4-Nitrophenyl α-D-galactopyranoside (PNP-alpha-D-Gal) is an artificial substrate of 4-nitrophenyl (pNP) glycopyranoside for detecting α-galactosidase activity. The amount of released pNP is significantly increased when 4-Nitrophenyl α-D-galactopyranoside is used as substrates.