Synthesis by enzymatic catalysis. III. Copolymerisation of amino acids and dipeptides using papain

After studying the oligomerisation reaction of L‐tyrosine, we investigated polymerisation of a mixture of methionine and tyrosine, which also led to the formation of a polypeptide. Various substrate concentrations and substrate/enzyme ratios were investigated. A hexapeptide was isolated containing three tyrosine and three methionine residues. Extension of the method to enzymatic polymerisation of dipeptide esters was also examined. After optimisation of the reaction, we obtained a peptide made up of four monomers using methyl L‐leucyl‐L‐tyrosinate as substrate. The results are discussed in the light of a possible reaction mechanism.