Chemical. CAS 35245-26-2. Formula C20H16ClNO3. MW BD9837. Naphthol AS-D chloroacetate NASDCA is a fluorigenic substrate for granulocyte specific esterases e.g. Proteinase 3 PR3 and Cathepsin G. It can be hydrolyzed into Naphthol AS-D by esterases to mix with diazonium salt and form insoluble red-brown precipitate in the cytoplasm that can be visualized under a microscope. This enzyme is usually considered specific for cells of granulocytic lineage. NASDCA can be used for the visualisation of cells in formalin-fixed or paraffin-embedded tissue in a substrate solution for naphthol-AS-D-chloroacetate-esterase CIAE staining. Proteinase 3 P3R is a serine protease that is found in neutrophils and a subpopulation of monocytes. It is the most specific enzyme for NASDCA hydrolysis, and it is used in a variety of diagnostic tests to detect granulocytes. Cathepsin G is another serine protease that is found in neutrophils.