The electron-transfer properties of H117G- and wild-type azurin were compared by applying both as electron accepters in the conversion of 1-ethylphenol by 4-ethylphenol methylenehydroxylase (4-EPMH... Show moreThe electron-transfer properties of H117G- and wild-type azurin were compared by applying both as electron accepters in the conversion of 1-ethylphenol by 4-ethylphenol methylenehydroxylase (4-EPMH). The reactivity of H117G-azurin was determined in the absence and presence of imidazoles, which can substitute the missing fourth ligand, In the absence of imidazoles, H117G-azurin reacted directly with 4-ethylphenol, this reaction was abolished in the presence of imidazoles, The enzymatic reduction of H117G-azurin by 4-EPMH was 40 times slower than that of wild-type azurin, The rate of this reaction was enhanced by some imidazoles, diminished by others. In all cases the reduction of H117G-azurin was irreversible. These results demonstrate that His117 is vital for electron transfer and effectively protects the copper site against aspecific reactions. Show less