MEMBRANES OF RETINAL MICROSOMES - A NEW-P ROTEIN OF THE MICROSOMAL MONOOXYGENASE SYSTEM

A new component, which substitutes cytochrome P-450 as an acceptor of reducing equivalents from NADPH-cytochrome P-450 reductase, was identi fied in bovine retina microsomal monooxigenase system, which does not contain cytochrome P-450. This component is a non-heme iron-containing protein with molecular mass of 66 kDa. The properties of the protein from bovine retina are similar to those of MIP, a non-heme iron-contai ning protein from heart microsomal monooxigenase system, in which cyto chrome P-450 also was not identified, The microsomal monooxigenase sys tem activation (increase in the NADPH-cytochrome P-450 reductase activ ity, an increased rate of microsomal NADPH oxidation) was shown in the retina upon long-term intensive illumination. It was found also that the development of hereditary degeneration of the retina in rats is ac companied by specific microsomal monooxigenase system activation in th e target tissues (retina, brain cortex) irrespectively of its composit ion (cytochrome P-450 or non-heme iron-containing protein).