Chitinases are chitin-degrading enzymes. Chitinases play essential roles in combating chitin-containing pathogens as well as established roles in asthmatic inflammation. This assay is designed to detect chitinase activity in macrophage cell lysates. The chitin substrate is labeled with 4-methylumbelliferone. Hydrolysis of chitin releases 4-methylumbelliferone, and is measured fluorometrically to determine chitinase activity.