This enzyme is specific for N-succinyl-L-ornithine and cannot use either L-ornithine (see EC 2.1.3.3, ornithine carbamoyltransferase) or N-acetyl-L-ornithine (see EC 2.1.3.9, N-acetylornithine carbamoyltransferase) as substrate. However, a single amino-acid substitution (Pro90 ¡ú Glu90) is sufficient to switch the enzyme to one that uses N-acetyl-L-ornithine as substrate. It is essential for de novo arginine biosynthesis in the obligate anaerobe Bacteroides fragilis, suggesting that this organism uses an alternative pathway for synthesizing arginine.
