Reaction: carbamoyl phosphate + N2-succinyl-L-ornithine = phosphate + N-succinyl-L-citrulline
Glossary: N-acetyl-L-citrulline = N5-acetylcarbamoyl-L-ornithine
Other name(s): succinylornithine transcarbamylase; N-succinyl-L-ornithine transcarbamylase; SOTCase
Systematic name: carbamoyl phosphate:N2-succinyl-L-ornithine carbamoyltransferase
Comments: This enzyme is specific for N-succinyl-L-ornithine and cannot use either L-ornithine (see EC 18.104.22.168, ornithine carbamoyltransferase) or N-acetyl-L-ornithine (see EC 22.214.171.124, N-acetylornithine carbamoyltransferase) as substrate. However, a single amino-acid substitution (Pro90 → 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.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:
1. Shi, D., Morizono, H., Cabrera-Luque, J., Yu, X., Roth, L., Malamy, M.H., Allewell, N.M. and Tuchman, M. Structure and catalytic mechanism of a novel N-succinyl-L-ornithine transcarbamylase in arginine biosynthesis of Bacteroides fragilis. J. Biol. Chem. 281 (2006) 20623-20631. [PMID: 16704984]
2. Shi, D., Yu, X., Cabrera-Luque, J., Chen, T.Y., Roth, L., Morizono, H., Allewell, N.M. and Tuchman, M. A single mutation in the active site swaps the substrate specificity of N-acetyl-L-ornithine transcarbamylase and N-succinyl-L-ornithine transcarbamylase. <>Protein Sci. 16 (2007) 1689-1699. [PMID: 17600144]