3-Indolyl 2-acetamido-2-deoxy-b-D-glucopyranoside is a substrate used for the detection of the enzyme N-acetylglucosaminidase (NAG). The enzyme hydrolyzes the NAG conjugate, releasing indole that can be detected through a colorimetric assay. This method is commonly used in clinical chemistry to evaluate kidney function, as NAG is excreted in urine and increased levels may indicate renal injury or disease. The indole NAG assay is also used in microbiology to detect the presence of NAG-producing bacteria.