Inhibits the PLA2 activity of crotoxin (CTX) by replacing the acid subunit (CA) in the CTX complex (PubMed:8195214, PubMed:1949070, PubMed:7851385, PubMed:10903514). Displays a pro-inflammatory action through activation of important main signaling pathways for human leukocytes, in vitro (PubMed:32183984). Abolishes both the muscle-paralyzing and muscle-damaging activities of CTX in mice phrenic nerve-diaphragm muscle preparations (PubMed:33387548). Occurs as a mixture of oligomers (PubMed:24820993). Tetrameric arrangement appears to be the predominant quaternary structure (PubMed:24820993). Interacts with phospholipase A2 crotoxin basic subunit CBd; the interaction leads to dissociation of the CA-CB heterodimer and to inhibition of PLA2 activity of the CB subunit (PubMed:10903514). Secreted in blood plasma. Expressed by the liver. The carbohydrate moiety increases the inhibition capacity of CNF, but is not essential for activity and for oligomerization. Belongs to the CNF-like-inhibitor family.