Ornithine cyclodeaminase

In enzymology, an ornithine cyclodeaminase (EC 4.3.1.12) is an enzyme that catalyzes the chemical reaction

L-ornithine L-proline + NH₄

Hence, this enzyme has one substrate, L-ornithine, and two products, L-proline and NH₄.

This enzyme belongs to the family of lyases, specifically ammonia lyases, which cleave carbon-nitrogen bonds. The systematic name of this enzyme class is L-ornithine ammonia-lyase (cyclizing; L-proline-forming). Other names in common use include ornithine cyclase, ornithine cyclase (deaminating), and L-ornithine ammonia-lyase (cyclizing). This enzyme participates in arginine and proline biosynthesis. It employs one cofactor, NAD+.

Structural studies

As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 1U7H and 1X7D.

References

• Costilow RN, Laycock L (1971). "Ornithine cyclase (deaminating). Purification of a protein that converts ornithine to proline and definition of the optimal assay conditions". J. Biol. Chem. 246 (21): 6655–60. PMID 4399881. 
• Muth WL, Costilow RN (1974). "Ornithine cyclase (deaminating). II. Properties of the homogeneous enzyme". J. Biol. Chem. 249 (23): 7457–62. PMID 4373469. 
• Espineda CE, Linford AS, Devine D, Brusslan JA (1999). "The AtCAO gene, encoding chlorophyll a oxygenase, is required for chlorophyll b synthesis in Arabidopsis thaliana". Proc. Natl. Acad. Sci. USA. 96 (18): 10507–11. doi:10.1073/pnas.96.18.10507. PMC 17919. PMID 10468639. 
• Goodman JL, Wang S, Alam S, Ruzicka FJ, Frey PA, Wedekind JE (2004). "Ornithine cyclodeaminase: structure, mechanism of action, and implications for the mu-crystallin family". Biochemistry. 43 (44): 13883–91. doi:10.1021/bi048207i. PMID 15518536. 
• Alam S, Wang SC, Ruzicka FJ, Frey PA, Wedekind JE (2004). "Crystallization and X-ray diffraction analysis of ornithine cyclodeaminase from Pseudomonas putida". Acta Crystallogr. D. 60 (Pt 5): 941–4. doi:10.1107/S0907444904005256. PMID 15103146.