Catalytic role of the active site histidine of porcine pancreatic phospholipase A2 probed by the variants H48Q, H48N and H48K.

The catalytic contribution of His48 in the active site ofporcine pancreatic phospholipase A2 was examined usingsite-directed mutagenesis. Replacement of His48 by lysine(H48K) gives rise to a protein having a distorted lipidbinding pocket. Activity of this variant drops below thedetection limit which is 10