Possible Role of Proteolytic Enzymes in Protein Synthesis

BERGMANN 1 has proposed that proteolytic enzymes mediate in the biological synthesis of proteins from amino-acids. The 400–4,000 2 or more 3 calories per mole required for peptide bond formation from free amino-acids can, however, be provided only when synthesis is coupled with an energy-yielding reaction 4 . To accommodate this energy requirement, Brenner, Hanes, Fruton and co-workers 4 a have demonstrated that a variety of proteolytic enzymes catalyse a reaction of esters, amides, or peptides (including the naturally occurring peptide, glutathione) with amines or amino-acids in which new amides or peptides are formed. The enzymes show their usual specificity; that is, they synthesize only those peptide bonds that they also hydrolyse. The energy requirement is met by the initial ester, amide or peptide linkage which is split, for there is presumably very little difference in energy between the bond destroyed and that formed. These workers have shown beyond doubt that some or perhaps most proteolytic enzymes can catalyse polypeptide synthesis from amino-acids, providing there is an independent method of ‘energizing’ the amino-acid (ester, amide, peptide, etc.). From there it is possible to speculate that in a similar way these proteolytic enzymes play a part in normal protein synthesis.