Is phospholipase in vinegared oysters a casual agent for human poisoning?

In this survey, lipid metabolism and activities of the lipolytic enzymes diglyceride lipase (DLase) and phospholipase A (PLase A) in the oyster digestive glands (ODGs), with 4% added acetic acid (the same acid concentration as vinegar) and incubated at 37 degrees C for 3 h, were investigated. Significant decreases in triglyceride, phosphatidycholine, and phosphatidylethanolamine and increases in monoglyceride, lysophosphatidylcholine, and lysophosphatidylethanolamine were observed in the acetic acid-treated ODGs. Changes in ODGs treated with PBS were smaller than in the acetic acid-treated ones but larger than in the nontreated ones. Both PLase A1, and PLase A2 in ODGs were activated by addition of acetic acid and incubated at 37 degrees C for 3 h. PLase A1 activities were higher than those of PLase A2, in all experimental ODGs. Addition of formic acid also induced activation of PLase A at pH 2. On the other hand, DLase in ODGs decreased remarkably with acetic acid treatment. These data showed that the increase in lipid metabolites such as free fatty acids and lysophospholipids in the acetic acid-treated ODGs might be due to catabolism of PLase A, which was activated by the acid treatment at 37 degrees C.