The interaction of a polymeric persimmon proanthocyanidin fraction with Chinese cobra PLA2 and BSA

To elucidate the anti-venom mechanism of persimmon tannin, the interaction between a polymeric persimmon proanthocyanidin fraction (PT40) and phospholipase A2 (PLA2) or bovine serum albumin (BSA) were studied using a competitive binding assay and spectroscopic methods including Fourier transform infrared spectroscopy (FT-IR), circular dichroism (CD), and resonance light scattering (RLS) spectroscopy. The results revealed that PT40 has a higher affinity for PLA2 than for BSA at physiological pH and induced greater conformational changes in PLA2 than in BSA. PT40 covalently bound to PLA2 in a reaction probably involving Lys residues. We propose that the high affinity of PT40 for PLA2 and the covalent modification of PLA2 by PT40 may be responsible for the ability of the tannin to irreversibly inhibit PLA2 catalytic activity, to prevent edema, and to neutralize the lethality of Chinese cobra PLA2 in vivo.