Purification and partial characterization of phospholipase A2 isoforms from human placenta.

Five isoforms of the human placental phospholipase A2 were identified and purified to near homogeneity. The purification of these enzymes involved gel permeation, ion-exchange and affinity chromatography. The apparent relative molecular mass of these proteins is 70,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These enzymes have pH optima of 7 and 8. Two-dimensional gel electrophoresis of these enzymes revealed distinct pH optima for each of the isoforms with values ranging from 4.0 to 6.5. Three of the isoforms require calcium for activity whereas the other two forms exhibit 50% of their maximum activity without the presence of calcium.