This compound, 4-Methylumbelliferyl 2-acetamido-2-deoxy-β-D-galactopyranoside (also known as 4-MU-β-GalNAc), is a fluorogenic substrate widely used in enzymatic assays to detect and measure the activity of β-N-acetylgalactosaminidase and β-hexosaminidase enzymes. It is particularly valuable in biochemical research and diagnostics for identifying enzyme deficiencies in biological samples. Upon cleavage by these enzymes, it releases the fluorescent product 4-methylumbelliferone, which can be quantified using fluorescence spectroscopy. This makes it essential for studying enzyme kinetics, screening inhibitors, and diagnosing lysosomal storage disorders such as Tay-Sachs disease and Sandhoff disease. Additionally, it is used in microbiology to differentiate bacterial species based on their enzymatic capabilities.