Inhibition of protein synthesis by products of lipid peroxidation

Effects of lipid peroxidation products on in vivo and in vitro protein synthesis have been studied. Malondialdehyde (MDA), a product, and a routinely used index of lipid peroxidation, inhibits in vivo protein synthesis in the two mosses, Tortula ruralis and Cratoneuron filicinum, and in pea (Pisum sativum) leaf discs. When wheat germ supernatant or poly(A)-rich mRNA of T. ruralis was incubated with MDA its subsequent activity in a cell-free protein-synthesizing system was reduced. When MDA was added directly to the in vitro protein-synthesizing mixture containing moss polyribosomes, the inhibition of amino acid incorporation was small. However, when simultaneous lipid peroxidation was allowed to occur along with in vitro protein synthesis there was a strong inhibition of amino acid incorporation and MDA accumulated in the reaction mixture indicating that products of lipid peroxidation other than, and apparently more toxic than, MDA were involved. It was concluded that lipid peroxidation inhibits protein synthesis probably by releasing toxic products which may react with and inactivate some components of the protein-synthesizing complex.