Phospholipase A2 isoenzyme from porcine pancreas. Purification and some properties.

Porcine pancreas synthesizes a prephospholipase A2 which occurs in a 5 : 95 ratio compared with the more abundant zymogen of the same enzyme (phosphatide-acylhydrolase; EC 3.1.1.4). These two prephospholipases could be well separated by CM-cellulose chromatography. Both the active and the zymogen form of the isoenzyme were isolated and purified. The activation peptides of both prephospholipases appeared to be identical, while the active enzymes showed a few interesting differences. The most striking differences were the loss of one histidine and one methionine in the isoenzyme, corresponding to residues 24 and 27, respectively, in alpha-phospholipase A2. The positional and stereo specificity of both enzymes are the same, but the specific activity of the beta-phospholipase A2 is lower. The molecular weight of the isoenzyme was estimated to be about 14 000, while the isoelectric points were 5.1 and 5.9 for the isoprecursor and active isoenzyme, respectively.