4-Methylumbelliferyl 2-acetoamido-2-deoxy-α-D-galactopyranoside (4-MU-2-acetoamido-2-deoxy-α-Gal) is a fluorogenic substrate used to quantify α- and β-galactopyranosaminidase activity. 4-MU-2-acetoamido-2-deoxy-α-Gal is cleaved by α- and β-galactopyranosaminidase to release the fluorescent moiety 4-MU. 4-MU fluorescence is pH-dependent with excitation maxima of 320 and 360 nm at low (1.97-6.72) and high (7.12-10.3) pH, respectively, and an emission maximum ranging from 445 to 455 nM, increasing as pH decreases.
