Monomer: Snake venom phospholipase A2 (PLA2) that shows a high PLA2 activity (2110 umol/min/mg). Heterodimer (A and B chains): snake venom phospholipase A2 that shows a moderate PLA2 activity (1377 umol/min/mg). Acts as a presynaptic neurotoxin. In vivo, induces edema and produces neurotoxic symptoms in mice. It exhibits indirect hemolysis and a strong myonecrotic activity and is cytotoxic. PLA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides. a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1-acyl-sn-glycero-3-phosphocholine + a fatty acid + H(+) Binds 1 Ca(2+) ion. Heterodimer of an acidic protein having phospholipase A2 activity (B chain) and an A chain which weakly inhibits the B chain enzymatic activity but potentiates its lethal potency. Expressed by the venom gland. Monomer: LD(50) of DbTx-B alone is estimated to be 0.5 ug/g by intraperitoneal injection into mice. Heterodimer (A and B chains): LD(50) is estimated to be about 0.1 ug/g by intraperitoneal injection into mice. Does not provoke hemorrhage. Belongs to the phospholipase A2 family. Group II subfamily. D49 sub-subfamily.