4-Methylumbelliferyl-a-D-Galactopyranoside

4-Methylumbelliferyl-a-D-galactopyranoside (4-MU-a-Gal) is a fluorogenic substrate of a-galactosidase.{33136,33137} In addition to its use in characterizing novel a-galactosidases, 4-MU-a-Gal is used in assays to evaluate deficiency in a-galactosidase activity related to Fabry disease.{33138} Hydrolysis of 4-MU-a-Gal releases the fluorescent product 4-MU, which has an emission maximum at 445-454 nm. The excitation maximum for 4-MU is pH-dependent: 330, 370, and 385 nm at pH 4.6, 7.4, and 10.4, respectively.{27251}