[Specificity of neutral ribosomal protease].

The specificity of the ribosomal proteinase was studied using a variety of substrates: nascend peptides, ribosomal proteins, B-chain of insulin and some synthetic peptides (the heptapeptide Gly-Phe-Phe-Tyr-Thr-Pro-Lys; the hexapeptide Gly-Phe-Leu-Gly-Phe-Leu and the CBZ-hexapeptide; the tripeptide Phe-His-Leu and the CBZ-tripeptide). It was shown that in the heptapeptide tested the enzyme cleaved most rapidly the Phe-Tyr bond; the Phe-Phe bond was cleaved less rapidly. The rest of the peptide bonds in the heptapeptide were also cleaved and by the end of the incubation the cleavage was complete. All the other substrates tested also underwent complete degradation. The data obtained allowed us to classify the enzyme with the group of endopeptidases with broad specificity of action. The possibility cannot be excluded that the broad specificity observed is due to the presence of more than one enzyme on the polyribosomes.