Modification of Amino Groups in Inhibitors of Proteolytic Enzymes^*

The interaction of guanidinated lima bean inhibitor with trypsin

“…In conformity with earlier studies [ 1,4,8], the combination of native LBI with trypsin was found to be nearly stoichiometric at pH 8 when correction was made for the fraction of inactive trypsin ( fig. 1).…”

“…This appears to be justified in the present case in view of the close similarity of the four variants in molecular size and amino acid composition, the identity of their susceptible peptide bonds, and the essential equivalence of the kinetics and equilibria of their interaction with trypsin [4,8,14].…”

“…It has recently been reported that guanidination of LBI fails to remove inhibitor activity and, in fact, increases the rate of combination [8]. This treatment converts lysine to homoarginine [9].…”

“…The modified form was produced by prolonged incubation with trypsin at pH 3.15 and 25°C [8]. The degree of conversion was assessed by treatment with carboxypeptidase B at pH 8 (see Methods) according to the procedure suggested by Krahn and Stevens [8].…”

“…The degree of conversion was assessed by treatment with carboxypeptidase B at pH 8 (see Methods) according to the procedure suggested by Krahn and Stevens [8]. II II II II II II I I II II II I I I I I indicates that less than one unreacted lysine remains per molecule.…”