In enzymology, a N5-(carboxyethyl)ornithine synthase (EC 1.5.1.24) is an enzyme that catalyzes the chemical reaction

N₅-(L-1-carboxyethyl)-L-ornithine + NADP⁺ + H₂O ${\displaystyle \rightleftharpoons }$ L-ornithine + pyruvate + NADPH + H⁺

The 3 substrates of this enzyme are N5-(L-1-carboxyethyl)-L-ornithine, NADP⁺, and H₂O, whereas its 4 products are L-ornithine, pyruvate, NADPH, and H⁺.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donors with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is N5-(L-1-carboxyethyl)-L-ornithine:NADP+ oxidoreductase (L-ornithine-forming). Other names in common use include 5-N-(L-1-carboxyethyl)-L-ornithine:NADP+ oxidoreductase, and (L-ornithine-forming).

• Thompson J (June 1989). "N5-(L-1-carboxyethyl)-L-ornithine:NADP+ oxidoreductase from Streptococcus lactis. Purification and partial characterization". The Journal of Biological Chemistry. 264 (16): 9592–601. PMID 2498334.