CHIT1:chitinase 1 (chitotriosidase). Chitotriosidase is a 50 kDa secreted glycoprotein that belongs to glycohydrolase family # 18. It is secreted by activated human macrophages and is markedly elevated in plasma of Gaucher disease patients. The expression of chitotriosidase occurs only at a late stage of differentiation of monocytes to activated macrophages in culture. Human macrophages can synthesize a functional chitotriosidase, a highly conserved enzyme with a strongly regulated expression. This enzyme may play a role in the degradation of chitin-containing pathogens.