Purification and properties of an active site mutant, H48Q, of human non-pancreatic secreted phospholipase A2.

A large number of I4kDa secreted phospholipases A, (sPLA,) have now been identified from venom and mammalian sources. Where solved, these enzymes show similar crystal structures including an active site containing a catalytic dyad of aspartic acid and histidine. In contrast to many lipases and serine proteases, a reactive serine is not utilised as part of the reaction mechanism and an acyl-enzyme intermediate is not involved. The essential nature of the catalytic histidine (His-48) in these enzymes was established at an early stage as this residue is sensitive to inactivation by pbromophenacyl bromide.