SITE-SPECIFIC INTRODUCTION OF AN ELECTROACTIVE LABEL INTO A NON-ELECTROACTIVE ENZYME (BETA-LACTAMASE-I)

A cysteine residue was introduced close to the active site of beta-lac tamase I by site-directed mutagenesis to replace tyrosine-105 and was subsequently modified with an electroactive SH-specific reagent, N-(2- ferrocene-ethyl)maleimide. The resulting modified enzyme became electr oactive, showing good quasireversible electrochemistry which was chara cteristic of the attached ferrocene moiety while retaining its specifi c enzymatic activity. In the presence of a suicide substrate, 6 beta-i odopenicillanic acid, the redox potential shifted +20 mV suggesting th at the label was sensitive to changes in the active site of the enzyme .