Post-heparin serum lecithinase in man and its positional specificity.

Lecithinase activity in post-heparin serum has been demonstrated. Phosphatidyl choline (PC) can be degraded to lysophosphatidyl choline and fatty acids at a rate of more than 1 micromole/hr per ml of serum in an incubation system containing PC, 0.1 M glycine-NaOH buffer (pH 9.6), and deoxycholate. This activity cannot be found in serum obtained prior to the injection of heparin. Post-heparin serum lecithinase can be distinguished from the heat-stable pancreatic lecithinase by the markedly different effects of heat, paraoxon, and EDTA, and from serum lecithin:cholesterol acyltransferase by the differential effect of p-hydroxymercuribenzoate. In contrast to the acyltransferase and to pancreatic lecithinase, which are active at the beta (C-2) position of lecithin, post-heparin serum lecithinase is active at alpha' (C-1) position.