Characterization of a phospholipase A2 in human serum.

Elevated catalytic activities of serum phospholipase A2 were measured in patients with inflammatory diseases. In contrast to human pancreatic phospholipase A2, the enzyme in serum of patients with non-pancreatic diseases was rather heat labile and showed a broad pH-optimum in the neutral range. Molecular sieving experiments revealed the existence of macro-molecular forms of the enzyme in serum which were cleaved into monomers of M(r) 14,000 in the presence of high salt concentrations. More than 100-fold purification was achieved by gel filtration chromatography on Sephadex G-100 in the presence of 2 mol/l KCl. Whether this serum phospholipase A2 and a secretory liver and platelet isoenzyme are identical remains to be established.