Proteins damaged by XXXX radicals are rapidly degraded in extracts of red blood cells.

@entity2656 @entity8798 @entity274 @entity3624 @entity620 @entity26 @entity16 @entity95 @entity3902 @entity653 @entity3787 @entity855 @entity1432 @entity141 @entity7482 @entity2145 @entity68 @entity3094
We have suggested that red blood cell proteolytic systems can degrade oxidatively damaged proteins, and that both damage and degradation are independent of lipid peroxidation (Davies, K. J. A., and Goldberg, A. L. (1987) J. Biol. Chem. 262, 8220-8226. These ideas have now been tested in cell-free extracts of @entity95 erythrocytes and reticulocytes. Exposure to @entity26 radicals or @entity274 increases the degradation of endogenous proteins in cell-free extracts, as in intact cells. Various radical-generating systems ( @entity3094 or @entity3624 + @entity3624 oxidase, @entity620 + @entity68 , @entity274 + @entity68 ) and @entity274 alone enhanced the rates of proteolysis severalfold. Since these extracts were free of membrane lipids, @entity16 and degradation must be independent of lipid peroxidation. An antioxidant buffer consisting of @entity7482 , @entity653 , and @entity3902 inhibited the increased proteolysis by 60-100%. @entity2656 caused a 50-80% reduction in proteolysis suggesting that the @entity3787 radical (. @entity2145 ), or a species with similar reactivity, may be the initiator of @entity16 . When casein or bovine serum albumin were exposed to . @entity2145 (generated by @entity274 + @entity8798 , or COCo radiation) these proteins were degraded up to 50 times faster than untreated proteins during subsequent incubations with red cell extracts. @entity2656 inhibited this increase in proteolysis only if present during . @entity2145 exposure; @entity2656 did not affect the degradative system. Although @entity855 increased the degradation of untreated proteins 4- to 6-fold in reticulocyte extracts, it had little or no effect on the degradation of proteins exposed to . @entity2145 . @entity855 also did not stimulate hydrolysis of @entity2145 -treated proteins in erythrocyte extracts. Leupeptin did not affect the degradative processes in either extract; thus lysosomal or @entity141 -activated @entity1432 proteases were not involved. We propose that red cells contain a soluble, @entity855 -independent proteolytic pathway which may protect against the accumulation of proteins damaged by . @entity2145 or other active @entity26 species.
