Catalyzes the transamination of N(2)-succinylornithine and alpha-ketoglutarate into N(2)-succinylglutamate semialdehyde and glutamate. Can also act as an acetylornithine aminotransferase. Is involved in the utilization of arginine as a nitrogen source, via the AST pathway, and seems also to play a role in ornithine catabolism (PubMed:9696779). 2-oxoglutarate + N(2)-succinyl-L-ornithine = L-glutamate + N-succinyl-L-glutamate 5-semialdehyde Amino-acid degradation; L-arginine degradation via AST pathway; L-glutamate and succinate from L-arginine: step 3/5. Its expression is under nitrogen control; a nitrogen-limited medium highly increases succinylornithine transaminase activity. Cells lacking this gene lose the ability to grow on arginine as the nitrogen source. The disruption of this gene also impairs ornithine catabolism. Belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family. AstC subfamily.