Pepsin behavior as a catalyst in equilibrium-controlled peptide synthesis

It has been shown that in the course of equilibrium peptide synthesis pepsin gradually disappeared from the liquid phase due to its entrapment within a gel formed by the hexapeptide product, while retaining its activity. The inclusion into the precipitate was not specific for pepsin so far as inert proteins-lysozyme, ribonuclease A and carbonic anhydrase, when added to the reaction mixture, became also co-precipitated with the hexapeptide formed. It appears that co-precipitation of pepsin-an important factor limiting the enzyme efficiency, might be operative as well for other proteinases used to catalyze peptide synthesis.