Inactivation of the Antibiotic Activity of Penicillin by Cysteine Hydrochloride. I. Chemical Aspects of Inactivation

Abstract

Summary

The antibiotic activity of penicillin can be easily abolished by cysteine in a slightly alkaline solution. The rate of inactivation is dependent on the amount of cysteine and pH. In an atmosphere of nitrogen, one mg of penicillin can be inactivated by several mg of cysteine at pH 7.8, but to a lesser extent with thioglycolic acid. Inactivation of penicillin does not take, place if other amino acids, e. g. cystine, methionine, serine, or glycine are used. Hence we believe that the inactivation of penicillin by cysteine is a chemical reaction and that it may involve both sulfhydryl and amino groups of cysteine.