Abstract Peptides with amino-terminal glutamine and their derivatives on treatment with crude papain preparation, containing glutaminyl-tRNA cyclotransferase (EC 2.3. 2.5.), are converted into the corresponding compounds with pyroglutamic acid. This enzymic cyclization does not take place with glutamic acid or its γ-derivatives. The reaction has been optimized for the preparation of pyroglutamic acid phenylhydrazide. Glutaminyl-leucine ...
