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