Application
Papain is also used for synthesizing poly(L-tyrosine) and poly(L-glutamic acid) using L-tyrosine ethyl ester hydrochloride and L-glutamic acid diethyl ester hydrochloride as the substrates, respectively. The protease-catalyzed copolymerization of amino acids is first achieved by papain using L-glutamic acid ester and various amino acid esters as substrates.
A mixture of L-tyrosine ethyl ester hydrochloride, the appropriate acid anhydri-des, triethylamine and dry tetrahydrofuran, was warmed for an hour in an atmosphere of nitrogen. After removing the amine salt, Ic and Id became crystalline on standing overnight in the cold.
Preparation
synthesis of L-Tyrosine Ethyl Ester Hydrochloride: Esterification of 25 g. ol L-tyrosine (0.014 mole) with ethanolic hydrogen chloride gave 24.1 g. of L-tyrosine ethyl ester hydrochloride (80%). Liberation of the ester by slurrying the hydrochloride in chloroform rollowed by the addition of chloroform saturated with ammonia, removal of the ammonium chloride by filtration and evaporation of the chloroform gave 19.4 g. of L-tyrosine ethyl ester (67%), m.p. 106-108 ° .
