Nafcillin was shown to reversibly inhibit beta-lactamase from Staphylococcus aureus PC1 with characteristics indicative of a type A inhibitor [Citri, Samuni & Zyk (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 1048-1052]. At nafcillin concentrations above 80 mM, complete inactivation occurred within 200 s. Upon removal of the excess nafcillin the inhibited enzyme was re-activated completely, with a rate constant of 2.0 x 10(-3) s-1 (25 degrees C). The inhibited enzyme was shown to be in the form of a covalent acyl-enzyme intermediate. Digestion by pepsin and trypsin yielded a single nafcillin-labelled peptide fragment which was isolated, sequenced and shown to be: Ala-Tyr-Ala-Ser-Thr-Ser-Lys. This sequence corresponds to the region surrounding the active-site serine residue, Ser-70, indicating that the inhibitor is covalently attached to the same residue as productive substrates.
Research Article|January 01 1992
Identification of the site of covalent attachment of nafcillin, a reversible suicide inhibitor of β-lactamase
A K Tan;
Biochem J (1992) 281 (1): 191-196.
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A K Tan, A L Fink; Identification of the site of covalent attachment of nafcillin, a reversible suicide inhibitor of β-lactamase. Biochem J 1 January 1992; 281 (1): 191–196. doi: https://doi.org/10.1042/bj2810191
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