Beta-Hexosaminidase (β-N-Acetylglucosaminidase, NAGase) Activity Colorimetric Assay provides a simple and sensitive method for monitoring hexosaminidase activity in biological samples (tissue, cells, serum, urine). This assay uses a synthetic p-nitrophenol derivative (R-pNP) as its substrate and releases pNP which can be measured at absorbance (OD 405 nm). The assay can detect as low as 50 µU of NAGase activity in a variety of samples.