8-Fluoro-8-Demethylriboflavin as a Potential Active-Site-Directed Reagent for Flavoprotein. Reaction with Some Amino Acids

Abstract

8-Fluoro-8-demethylriboflavin was shown to be a potential active-site-directed reagent for flavoproteins. It reacted with the nucleophiles of N-acetylcysteine (-SH), N-acetyltyrosine (-OH), a-N-acetyllysine, and glycine (ε- and a-NH₂, respectively) under fairly mild conditions, and the reaction products were identified. The reactivity of the fluoroflavin was higher than that of 8-chloro-8-demethylribo-flavin, which reacted only with the cysteine derivative among the amino acid derivatives used, and whose pseudo first order rate constant at 23°C was 1/23 of that of the fluoroflavin. The reactivity of the fluoroflavin was also estimated by ¹³C and ¹⁹F NMR spectroscopy. The results showed that this compound is more reactive than the chloroflavin.