Key points are not available for this paper at this time.
Modification of E-64 focused on the terminal agmatine for practical use led to some potent analogs which were successfully obtained by a stereoselective synthesis using D-tartaric acid as a starting material. Ep-475 (id. E-64-c), in which the agmatine was replaced by 3-methyl-butylamine, was found to react with the essential SH of papain in accord with the decrease of activity. 3HEp-475 was irreversibly incorporated into papain in an equimolar ratio. None of the analogs showed any effect on thiol enzymes other than proteolytic ones.
Tamai et al. (1981) studied this question.