Identification and characterization of phospholipase A2 inhibitors from the serum of the Japanese rat snake, Elaphe climacophora

Two distinct phospholipase A2 (PLA2) inhibitory proteins (PLIs) were purified from the serum of the Japanese rat snake, Elaphe climacophora. The 150-kDa inhibitor, a trimer of a 50-kDa subunit, specifically inhibited the basic PLA2 purified from the venom of Gloydius brevicaudus, whereas the 120-kDa one composed of two distinct 25-kDa subunits, A and B, inhibited both the acidic and basic PLA2s of G. brevicaudus. On the basis of their amino acid sequences, these inhibitors were assigned as PLIβ and PLIγ, respectively. A PLIα homolog (PLIα-like protein; PLIα-LP) having an apparent molecular weight of 50-kDa and composed of 15-kDa subunits was also purified from the E. climacophora serum. This homolog was immunoreactive with antibody raised against the G. brevicaudus PLIα, but lacked in the inhibitory activity toward the acidic and basic PLA2s. The cDNAs encoding PLIα-LP, PLIβ, PLIγ-A, and PLIγ-B were cloned from liver RNA, and their nucleotide sequences were compared with those of other venomous and non-venomous snakes.