Chitotriosidase-1 (CHIT1) is a glycoprotein that belongs to the Glycosyl Hydrolase 18 family and Chitinase class II subfamily. It is secreted by cultured macrophages and serves to degrade chitin, chitotriose and chitobiose. CHIT1 may participate in the defense against nematodes and other pathogens. It is highly expressed in the plasma of patients with Gaucher's disease type I, which can be used as diagnostic aid and to evaluate the success of treatment that brings levels back to normal. The amino acid sequence of human CHIT1 is 99%, 76%, 75% and 55% identical to that of chimpanzee, rat, mouse and fruit fly, respectively.