DL-alpha-(Difluoromethyl)arginine: a potent enzyme-activated irreversible inhibitor of bacterial decarboxylases

DL-alpha-(Difluoromethyl)arginine (RMI 71 897) is an irreversible inhibitor of both the biosynthetic and biodegradative arginine decarboxylases of Escherichia coli and of the biosynthetic arginine decarboxylases of Pseudomonas aeruginosa and Klebsiella pneumoniae. The Ki is close to 800 muM for the biosynthetic decarboxylase of E. coli and 140 muM for the biodegradative Enzyme while the respective half-lives (t1/2) calculated for an infinite concentration of inhibitor are 1.0 and 2.1 min. The inhibitor also blocks the arginine decarboxylase activity of E. coli and Pseudomonas aeruginosa in vivo, indicating that the compound is transported into the cell. DL-alpha-Methylarginine (RMI 71 699) was found to be a competitive inhibitor of both arginine decarboxylases from E. coli. These results suggest that it may be possible to use an arginine decarboxylase inhibitor in conjunction with known inhibitors of ornithine decarboxylase to block all putrescine biosynthesis in prokaryotic cells and thus to study the effects of such inhibition in these organisms.