CHITINASE ACTIVITY IN HUMAN SERUM AND LEUKOCYTES

Using colloidal [H-3]chitin as a substrate, we provide the first demon stration of a chitinase in human leukocytes; chitinolytic activity in, whole and disrupted leukocyte preparations (approximately 0.6 and 5.5 nmol of N-acetylglucosamine [GlcNAc] released min(-1) mg of protein(-1 ), respectively) was partially inhibited by the specific chitinase inh ibitor allosamidin (9 mu M). Following fractionation of the leukocytes , much higher levels of chitinase activity were detected in granulocyt e-rich homogenates (approximately 7.2 nmol of GlcNAc released min(-1) mg of protein(-1)) than in lymphocyte- and monocyte-rich homogenates ( approximately 0.22 and 0.26 nmol of GlcNAc released min(-1) mg of prot ein(-1), respectively). Low levels of chitinase activity were detected in human serum (approximately 4 pmol of GlcNAc released min(-1) mg of protein(-1)). Chitinolytic activity in granulocyte-rich homogenates a nd serum was partially inhibited by allosamidin (9 mu M). Proteins wit h chitinolytic activities (approximate molecular masses, 48 and 56 kDa ) distinct from lysozyme (14.3 kDa) were detected on polyacrylamide ge ls following the electrophoresis of human granulocyte-rich preparation s, Chitinase activity, detected consistently in serum and leukocytes f rom all human volunteers investigated, may contribute to the protectio n of the host by cleaving chitin in the cell walls of fungal pathogens .