Identification of β-type phospholipase A2 inhibitor in a nonvenomous snake, Elaphe quadrivirgata

A novel serum protein inhibiting specifically the enzymatic activity of the basic phospholipase A2 (PLA2) from the venom of the Chinese mamushi snake (Agkistrodon blomhoffii siniticus) was purified from a nonvenomous Colubridae snake, Elaphe quadrivirgata. The purified inhibitor was a 150-kDa glycoprotein having a trimeric structure, composed of two homologous 50-kDa subunits. Their amino acid sequences, containing leucine-rich repeats, were typical of the β-type PLA2 inhibitor (PLIβ), previously identified from the serum of A. blomhoffii siniticus. The inhibitor inhibited exclusively group II basic PLA2s and did not inhibit other kinds of PLA2s. This is the first paper reporting the existence of PLIβ in a nonvenomous snake. The existence of PLIβ in the nonvenomous snake reflects that PLIβs are widely distributed over the snake species and participate commonly in regulating the physiological activities of the unidentified target PLA2s.