Active site of bee venom phospholipase A2: the role of histidine-34, aspartate-64 and tyrosine-87

The kinetic properties of honeybee venom phospholipase A2 (bvPLA2) mutants at the aspartate-64 and tyrosine-87 positions were examined by substitution with asparagine (D64N) or alanine (D64A), and replacement of the histidine active site residue with glutamine (H34Q) and tyrosine residue with phenylalanine (Y87F). H34Q is catalytically inactive whereas D64N, D64A and Y87F demonstrate good activity. The hydrogen-bonding network spanning tyrosine-87-aspartate-64-histidine-34 has no marked effect on the catalytic process.