Serine protease inhibitor that inhibits plasminogen activators and plasmin but not thrombin (  ). May be involved in the formation or reorganization of synaptic connections as well as for synaptic plasticity in the adult nervous system. May protect neurons from cell damage by tissue-type plasminogen activator (Probable).
Subcellular locations: Secreted, Cytoplasmic vesicle, Secretory vesicle lumen, Perikaryon
Detected in brain cortex and hippocampus pyramidal neurons (at protein level) . Detected in cerebrospinal fluid (at protein level) . Predominantly expressed in the brain .