Difluoromethylornithine irreversibly inactivates ornithine decarboxylase of Pseudomonas aeruginosa, but does not inhibit the enzymes of Escherichia coli

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Abstract
DL-.alpha.-Difluromethylornithine, an enzyme-activated irreversible inhibitor of eukaryotic ornithine decarboxylase and consequently of putrescine biosynthesis, inhibited ornithine decarboxylase in enzyme extracts from P. aeruginosa in a time-dependent manner with a t1/2 (half-time) of 1 min, and also effectively blocked the enzyme activity in situ in the cell. Difluoromethylornithine had no effect on the activity of ornithine decarboxylase assayed in enzyme extracts from either E. coli or Klebsiella pneumoniae. The presence of the inhibitor in cell cultures partially lowered ornithine decarboxylase activity intracellularly in E. coli. Any decrease in the intracellular ornithine decarboxylase activity observed in E. coli and P. aeruginosa was accompanied by a concomitant increase in arginine decarboxylase activity, arguing for a coordinated control of putrescine biosynthesis in these cells.