Comparison of peroxidases in the retina, choroid and red blood cells.

Most of the peroxidase activity in the bovine retina is specific to glutathione (GSH) while the choroid contains both GSH peroxidases and ascorbate peroxidase. The GSH peroxidase was clearly separated from ascorbate peroxidase on a cation exchange column. The nonspecific peroxidase activity of hemoproteins accounts for the peroxidase activity detected by ascorbate oxidation. All choroidal hemoproteins contain subunits very similar to those of hemoglobin. The absence of ascorbate peroxidase in the retina indicates that the protective effect of ascorbate against photic injury is not due to its reaction with retinal peroxidase. Therefore removal of H2O2 by ascorbate peroxidase activity in the choroid could be a significant factor in studies where serum ascorbate concentrations are artificially raised far above the normal level concurrent to a very small rise in retinal ascorbate concentration.