The effects of beta-endorphin and enkephalins on protein biosynthesis in a eukaryotic cell-free system. Inhibition of phenylalanyl-tRNA synthetase.

The effects of beta-endorphin and various enkephalins on protein synthesis in eukaryotic cell-free systems have been examined. Beta-Endorphin, Leu-enkephalin, and Met-enkephalin inhibit the incorporation of radioactive leucine into globin in the presence of reticulocyte poly(A)+ RNA and of radioactive phenylalanine into polyphenylalanine in the presence of poly(U); however, the poly(U)-dependent synthesis of polyphenylalanine from Phe-tRNA is not inhibited. the aminoacylation of tRNAPhe is markedly inhibited by enkephalin, indicating that the sensitive component is Phe-tRNA synthetase. Other aminoacyl-tRNA synthetases are not significantly affected. The interaction between enkephalin and Phe-tRNA synthetase is reversible; activity is restored by dialysis of enzyme-enkephalin reaction mixtures. Morphine, vasopressin and analogues of vasopressin, and enkephalin analogues such as [D-Ala2,D-Leu5]enkephalin and [D-Ala2,Met]enkephalinamide have no effect on translation. The results suggest that the effects on protein synthesis are probably not related to opiate effects.