This gene encodes a member of the serpin family that does not display the serine protease inhibitory activity shown by many of the other serpin proteins. The encoded protein is secreted and strongly inhibits angiogenesis. In addition, this protein is a neurotrophic factor involved in neuronal differentiation in retinoblastoma cells. Mutations in this gene were found in individuals with osteogenesis imperfecta, type VI. [provided by RefSeq, Aug 2016],developmental stage:Expressed in quiescent cells.,domain:The N-terminal (AA 44-121) exhibits neurite outgrowth-inducing activity. The C-terminal exposed loop (AA 382-418) is essential for serpin activity.,function:Neurotrophic protein, induces extensive neuronal differentiation in retinoblastoma cells. Potent inhibitor of angiogenesis. As it does not undergo the S (stressed) to R (relaxed) conformational transition characteristic of active serpins, it exhibits no serine protease inhibitory activity.,PTM:The N-terminus is blocked. Extracellular phosphorylation enhances antiangiogenic activity.,similarity:Belongs to the serpin family.,subcellular location:Enriched in stage I melanosomes.,tissue specificity:Retinal pigment epithelial cells and blood plasma.,
