Luigi Moroder

Enzymatic activity of partially synthetic ribonucleases

Abstract Synthetic peptides, which differ from the natural S-peptide obtained by proteolysis of ribonuclease A (ribonucleate pyrimidinenucleotido-2′-transferase (cyclizing), EC 2.7.7.16), are able to regenerate enzymatic activity when combined with the S-protein. The activity is either depolymerase on yeast nucleic acid or hydrolase on uridine 2′,3′-phosphate. The apparent dissociation constants of the different peptide-protein complexes are calculated, showing the influence of the primary structure on binding. The different behaviour of the reconstituted enzymes is illustrated by pH-activity curves.

Synthesis of peptides analogous to the N-terminal eicosapeptide sequence of ribonuclease A. Part III. A new synthesis of the C-terminal octapeptide 13–20

Synthesis is described of the octapeptide corresponding to the 13–20 sequence of the bovine pancreatic ribonuclease A. The pentapeptidebenzyloxycarbonyl-L-seryl-L-threonyl-L-seryl-L-alanyl-L-alanine t-butyl ester was built up by coupling, by the azide procedure, benzyloxycarbonyl-L-seryl-L-threonine hydrazide with L-seryl-L-alanyl-L-alanine t-butyl ester.The subsequent elongation to the octapeptide was carried out stepwise by the p-nitrophenyl ester method. Exposure of the protected peptide to trifluoroacetic acid yielded L-methionyl-L-aspartyl-L-seryl-L-seryl-L-threonyl-L-seryl-L-alanyl-L-alanine.