Evidence for functional involvement of asparagine 67 in substrate recognition by snake venom phospholipases A₂

Site-directed mutagenesis studies of recombinant Trimeresurus flavoviridis venom gland phospholipase A₂ (PLA₂) showed that the Asn residue at position 67 takes part in recognition of the substrate 2-arachidonoyl sn-glycero-3-phosphocholine in both monomeric and micellar states. The amount of arachidonate released from phosphatidylcholine mixed micelles was reduced to 30% for N67D and N67K mutants, and to 70% for N67G mutant, but remained unchanged for N67S mutant. In contrast, for monomeric substrate, the activity was decreased to 40% for N67D and N67G and to 60% for N67K but remained unchanged for N67S. These results suggest that the properties of the side chain of residue 67 exert a significant influence on recognition of 2-arachidonoyl sn-glycero-3-phosphocholine.