Binds ATP, opioids and phosphatidylethanolamine. Has lower affinity for phosphatidylinositol and phosphatidylcholine. Serine protease inhibitor which inhibits thrombin, neuropsin and chymotrypsin but not trypsin, tissue type plasminogen activator and elastase (By similarity). Inhibits the kinase activity of RAF1 by inhibiting its activation and by dissociating the RAF1/MEK complex and acting as a competitive inhibitor of MEK phosphorylation (By similarity). HCNP may be involved in the function of the presynaptic cholinergic neurons of the central nervous system. HCNP increases the production of choline acetyltransferase but not acetylcholinesterase. Seems to be mediated by a specific receptor (By similarity). Has a tendency to form dimers by disulfide cross-linking. Interacts with RAF1 and this interaction is enhanced if RAF1 is phosphorylated on residues 'Ser-338', 'Ser-339', 'Tyr-340' and 'Tyr-341'. Interacts with ALOX15; in response to IL13/interleukin-13, prevents the interaction of PEBP1 with RAF1 to activate the ERK signaling cascade (By similarity). Belongs to the phosphatidylethanolamine-binding protein family.