The identification and properties of chitin-binding protein b01 (CBPb01)

Bovine serum contains N-acetyl-D-glucosamine (GlcNAc)-sensitive opsonin inhibitory factors. In the present study, a major component of chitin-binding protein (chitin-binding protein b01, CBPb01) was purified from bovine serum, and identified CBPb01 as bovine IgM by its subunit structure, antigenic properties, and partial sequences. The results of a lectin-binding assay showed that the heavy chain of CBPb01 had a GlcNAc structure, but the commercial IgM did not. It is possible that CBPb01 interconnects through its GlcNAc structure, subsequently forming complexes. We also demonstrated that CBPb01 had opsonin-inhibitory activity, and that this activity was dependent on the binding of CBPb01 to GlcNAc on the zymosan surface. These findings indicate the presence of a kind of IgM that recognizes GlcNAc structure in the regulation of opsonization.