Carbon monoxide inhibits the anticoagulant activity of phospholipase A ₂ purified from Crotalus adamanteus venom

Snake venom contains a myriad of classes of enzyme which have been investigated for medicinal and toxinological purposes, including phospholipase A ₂ (PLA ₂ ), which is responsible for anticoagulant, myotoxic and neurotoxic effects. Given the importance of PLA ₂ , the purposes of the present investigation were to characterize the coagulation kinetic behavior of a PLA ₂ purified from Crotalus adamanteus venom (Ca-PLA ₂ ) in human plasma with thrombelastography and determine if carbon monoxide could inhibit its activity. Coagulation kinetics were determined in human plasma with a range of Ca-PLA ₂ activity (0–2 U/ml) via thrombelastography. Then, using carbon monoxide releasing molecule-2 or its inactivated molecule (0 or 100 µM), the vulnerability of Ca-PLA ₂ activity to carbon monoxide mediated inhibition was assessed. Lastly, the inhibitory response of Ca-PLA ₂ activity to exposure to carbon monoxide releasing molecule-2 (0–100 µM) was determined. Ca-PLA ₂ activity degraded the velocity of clot growth and clot strength in an activity dependent, exponential manner. Carbon monoxide inhibited Ca-PLA ₂ activity in a concentration dependent fashion, with loss of detectable activity at 100 µM of carbon monoxide releasing molecule-2. These findings, while preliminary, open the possibility that other PLA ₂ contained in snake venom with multiple toxicities (e.g., myotoxin, neurotoxin) may be heme bearing and CO-inhibitable, which have profound potential basic and clinical science implications.