Human Chitinase 3-like 2 Biotinylated Affinity Purified PAb

Chitinase 3-like 2 (CHI3L2), also called chondrocyte protein 39 or YKL-39, is a 39 kDa potentially glycosylated member of the glycosyl hydrolase 18 family (1‑3). It is secreted by synovial fibroblasts, chondrocytes, and TGF beta/IL-4-stimulated monocyte-derived macrophages (1, 4, 5). The human CHI3L2 cDNA encodes 390 amino acids (aa), including a 26 aa signal sequence and a 364 aa mature region. Potential alternate start sites at Met-24 and Met+80 would create isoforms of 413 aa and 311 aa, while a potential deletion of aa 15‑24 would create a 380 aa isoform (6). Mature human CHI3L2 shares 89%, 87% and 84% aa sequence identity with bovine, porcine and equine CHI3L2, respectively. The rodent genome does not include a CHI3L2 ortholog (2). Human CHI3L1 and CHI3L2 share 43% aa sequence identity. Neither shows chitotriosidase activity, but both bind chitin and are thus termed chi-lectins (1‑3). Unlike CHI3L1, CHI3L2 does not bind heparin (1). While CHI3L1 is the major protein excreted by chondrocytes, up-regulation of CHI3L2 and not CHI3L1 correlates with osteoarthritic cartilage degeneration (1, 7, 8). CHI3L2 has been proposed as a potential biomarker for osteoarthritis (4, 7, 8). CHI3L1 has been found to coordinate adhesion receptors and promote cell signaling and tumor angiogenesis; like CHI3L1, CHI3L2 can enhance cell adhesion (9).