A novel phosphatidylcholine hydrolysing action of C-reactive protein

We have observed a novel time and dose dependent stimulatory effect of CRP on the hydrolysis of dipalmitoyl phosphatidylcholine (DPPC) into phosphorylcholine (P-choline) and diacylglycerol (DAG). This effect was shared by rat, rabbit, human and asialo-rat CRP but not by other serum proteins, i.e., albumin, ovalbumin and alpha 1-acid glycoprotein. DPPC was also hydrolysed by normal rat serum (contains CRP) but not when serum was depleted of CRP. There is a requirement of Ca2+ for this unsuspected effect which was observed over a wide range of pH and the effect was markedly increased in temperatures up to 48 degrees C. The hydrolysis of DPPC showed a 3-fold decrease in Km when the assays included rat CRP. Massive increase of CRP in response to inflammation and its involvement in host defense reactions have been well documented. Significance of the present study rests on the possibility that the mechanism of action of CRP in cellular metabolism might be related to the production of DAG and P-choline known to have roles respectively in signal transduction and growth factor stimulated DNA synthesis.