Evidence of peroxidase activity of the peroxidation inhibiting protein on dilinoleyl phosphatidylcholine hydroperoxide as obtained in direct electron impact conditions

The recently purified peroxidation inhibiting protein (PIP) reduces, at the expense of glutathione oxidation, hydroperoxide groups of phospholipids. The mass spectral characterization in direct electron impact conditions of a high performance liquid chromatographic purified typical substrate of PIP (dilinoleyl phosphatidylcholine hydroperoxide) and its enzymatic reaction product is given on the basis of the fragmentation pattern of native dilinoleyl phosphatidylcholine. The results confirm the peroxidase activity of PIP and show that the direct electron impact technique is a suitable tool in mass spectrometric studies of large and thermolabile compounds as oxidation products of phospholipids.