Purification of phospholipid hydroperoxide glutathione peroxidase from bovine retina

A low molecular size peroxidase with a high affinity for phospholipid hydroperoxide was purified from bovine retina by sequential extraction with low and high ionic strength buffer, followed by ammonium sulfate fractionation, chromatography on an ultraspherogel column and Protein PAK-SP column. The purified enzyme has a low Km (0.011 mmol/L) for phospholipid hydroperoxide, and a high Km (1.37 mmol/L) for glutathione. Glutathione oxidation was competitively inhibited by vitamin E, Ki = 0.019 mmol/L. The retinal PHGPX is different from the PHGPX purified by others from heart and liver in molecular size. The molecular size estimated by gel filtration chromatography is below 6 kDa.