Mouse Testican 3/SPOCK3 Biotinylated Antibody

Testican 3 encoded by the SPOCK3 gene is a proteoglycan expressed in brain (1). The human and mouse cDNAs predict 90% identity between the deduced amino acid sequences from the two species, indicating a conserved function (2, 3). Only the human protein, but not the mouse protein, has been characterized in the literature. Testican 3 contains Ca²⁺-binding domain and the C-terminal acidic domain with putative glycosaminoglycan attachment sites. In addition, it contains three potential inhibitory domains targeted toward three different classes of proteases, metallo, cysteine and serine proteases. The N-terminal region, which is unique to testicans, is responsible for the inhibition of Testican 3 towards MMP-14 (MT1-MMP, a metalloprotease) activation of MMP-2 (1). The thyropin domain and the follistatin-like domain with a six cysteine Kazal-like motif may inhibit cysteine and serine proteases, respectively (4). A spliced variant designated as N-Tes contains the N-terminal unique region, the follistatin-like domain and the Ca²⁺-binding domain, but lacks the C-terminal thyropin domain and the acidic domain (1). The purified rmTestican 3 is capable of inhibiting rhMMP-14 and rhCathepsin L (R&D Systems, Catalog # 918-MP and 952-CY) in assays using the fluorogenic peptide substrates (R&D Systems, Catalog # ES001 and ES008). As compared to rhTestican 1 (R&D Systems, Catalog # 2327-PI), the IC₅₀ of rmTestican 3 is weaker toward rhCathepsin L and rhMMP-14 activity.