Heterodimer A-B: Nigroviriditoxin possesses phospholipase A2 (PLA2) activity. It consists of a non-covalent association of a basic PLA2 subunit B with a non-enzymatic subunit A. Subunit B: Snake venom phospholipase A2 (PLA2) that induces myonecrosis in mice. 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. Nigroviriditoxin is a heterodimer of an acidic subunit A and a basic subunit B. Expressed by the venom gland. LD(50) is 2.9 mg/kg by intravenous injection in mice. Toxicity is higher in combination with subunit A. Belongs to the phospholipase A2 family. Group II subfamily. D49 sub-subfamily.