N 2 -Succinylated intermediates in an arginine catabolic pathway of Pseudomonas aeruginosa

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Abstract
Arginine-nonutilizing ( aru ) mutants of Pseudomonas aeruginosa strain PAO converted L-arginine to N 2 -succinylarginine or N -succinylglutamate, which were identified by high-voltage electrophoresis and HPLC. Addition of aminooxyacetate, an inhibitor of pyridoxal phosphate-dependent enzymes, to resting cells of the wild-type PAO1 in arginine medium led to the accumulation of N 2 -succinylornithine. Enzyme assays with crude P. aeruginosa extracts established the following pathway: L-arginine + succinyl-CoA → N 2 -succinylarginine → N 2 -succinylornithine → N _succinylglutamate 5-semialdehyde → N -succinylglutamate → succinate + glutamate. Succinyl-CoA may be regenerated from glutamate via 2-ketoglutarate. L-Arginine induced the enzymes of the pathway, and succinate caused catabolite repression. Purified N 2 -acetylornithine 5-aminotransferase ( N 2 -acetyl-L-ornithine: 2-oxoglutarate aminotransferase, EC 2.6.1.11), an arginine biosynthetic enzyme, efficiently transaminated N 2 -succinylornithine; this explains the enzyme's dual role in arginine biosynthesis and catabolism. The succinylarginine pathway enables P. aeruginosa to utilize arginine efficiently as a carbon source under aerobic conditions, whereas the other three arginine catabolic pathways previously established in P. aeruginosa fulfill different functions.