Testican3, also called SPOCK3, is a secreted protein and make up a family of extracellular heparan/chondroitin sulfate proteoglycans. It contains 1 Kazal-like domain and 1 thyroglobulin type-1 domain. Testican3 contain inhibitory regions in several domains targeted to different classes of protease, and in some cases may act as protease inhibitors. In addition to their presence in testis, testicans are enriched in brain and have been shown to regulate neuronal attachment and outgrowth. It may participate in diverse steps of neurogenesis and Inhibits the processing of pro-matrix metalloproteinase 2 (MMP-2) by MT1-MMP and MT3-MMP. It also may interfere with tumor invasion.