Enzymatic reduction of polyunsaturated lysophosphati‐dylcholine hydroperoxides by glutathione peroxidase‐1

Abstract

AbstractSome lipid peroxides are known to be converted to their corresponding alcohols in cells containing glutathione peroxidase (GPx). In this respect, we examined the enzymatic conversion of lysophosphatidylcholine (lysoPC) hydroperoxides to hydroxyl derivatives using RBL‐2H3 cells and erythrocyte GPx‐1. First, the incubation of RBL‐2H3 cells with arachidonoyl lysoPC led to the formation of a major product, with maximal UV absorbance at 234 nm and m/z [M+H]+ at 560.2, corresponding to monohydroxyeicosatetraenoyl lysoPC. Similarly, linoleoyl lysoPC was also converted to its hydroxyl derivative in RBL‐2H3 cells. Separately, lysoPC hydroperoxide, generated from soybean lipoxygenase 1‐catalyzed oxygenation of linoleoyl lysoPC, arachidonoyl lysoPC or docosahexaenoyl lysoPC, was converted by GPx‐1 to the corresponding hydroxyl derivatives. When the kinetic values were determined, the Km values (3.1–32.3 µM) of the polyunsaturated lysoPC hydroperoxides increased with decreasing number of double bonds, in contrast to a similar value of Vm among them. Moreover, the catalytic efficiency of docosahexaenoyl lysoPC hydroperoxide was much greater than that of H2O2 as substrate of GPx‐1. In related experiments, where phosphatidylcholine hydroperoxides were incubated with phospholipase A2 and GPx‐1, the complete conversion of phosphatidylcholine hydroperoxides to hydroxyl derivatives was confirmed by LC/MS. Taken together, it is proposed that GPx‐1‐type enzymes may participate in the conversion of polyunsaturated lysoPC hydroperoxides to hydroxyl derivatives in cell systems.