PEPTIDE-SYNTHESIS BY CHYMOTRYPSIN IN FROZEN-SOLUTIONS - FREE AMINO-ACIDS AS NUCLEOPHILES

Nucleophilic efficiency of free amino acids in chymotrypsin-catalyzed acyl transfer in ice at -18-degrees-C using ethyl esters of N-maleyl-L -tyrosine and L-tyrosine as the acyl group donors has been studied. Al though the amino acids did not act as acyl acceptors in liquid water, the high yields of peptides were obtained in frozen solutions at pH 10 .5 (before freezing). The efficiency of amino acids in the formation o f the corresponding dipeptides depended on the substrate used, and dec reased in the order er,Thr,Gln>Lys>Cit>Ala>Gly>Asn>Arg>Glu>Val>Orn>Asp (with no peptide formed with His, Leu, Ile and Pro) for N-maleyl-L-ty rosine ethyl ester and Ser>Lys>Orn>Arg,Cit>Gln>Thr>Asn>Ala>Gly (with n o peptide formed with Glu, Val, Asp, His, Leu, Ile and Pro) for L-tyro sine ethyl ester.