Enzymatic characterization of a novel phospholipase A2 from Crotalus durissus cascavella rattlesnake (Maracambóia) venom

Abstract

The PLA2 and crotapotin subunits of crotoxin from Crotalus durissus cascavella venom were purified by a combination of high-performance liquid chromatography (HPLC) molecular exclusion (Protein Pack 300SW column) and reverse-phase HPLC (RP-HPLC). Tricine SDS-PAGE showed that the PLA2 and crotapotins migrated as single bands with estimated molecular masses of 15 and 9 kDa, respectively. The amino acid composition of the PLA2 showed the presence of 14 half-cysteines and a high content of basic residues (Lys, Arg, His), whereas the crotapotins were rich in hydrophobic, negatively charged residues and half-cysteines. The PLA2 showed allosteric behavior, with maximal activity at pH 8.3 and 35-40 degrees C. C. d. cascavella PLA2 required Ca2+ for activity but was inhibited by Cu2+ and Zn2+ and by Cu2+ and Mg2+ in the presence and absence of Ca2+, respectively. Crotapotin (F3) and heparin inhibited the catalytic activity of the PLA2 by acting as allosteric inhibitors.