The enzyme ornithine cyclodeaminase (EC 4.3.1.12) catalyzes the chemical reaction L -ornithine L -proline + 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 and.