Purification and partial characterization of a bacterial phospholipid: cholesterol acyltransferase

A glycerophospholipid:cholesterol acyltransferase has been purified to near homogeneity from cell-free culture supernatants of Aeromonas salmonicida. The characteristics of the enzyme distinguish it from bacterial phospholipases; however, it shares several properties with the lecithin:cholesterol acyltransferase of mammalian plasma. Thus, the enzyme inhibits 2-positional specificity as an acyltransferase and it will act as a phospholipase A2 in the absence of cholesterol. Furthermore, it has no divalent cation requirement and it is stimulated both by albumin and by human apolipoprotein A-I. Unlike the mammalian acyltransferase, however, the bacterial enzyme is not specific for phosphatidylcholine and in addition it can use human erythrocyte membranes as substrates. Similar to Naja naja phospholipase A2, it acts asymmetrically on intact erythrocytes.