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N(5)-(carboxyethyl)ornithine synthase N(5)-(carboxyethyl)ornithine synthase (ceo_syn) catalyzes the NADP-dependent conversion of N5-(L-1-carboxyethyl)-L-ornithine to L-ornithine + pyruvate. Ornithine plays a key role in the urea cycle, which in mammals is used in arginine biosynthesis, and is a precursor in polyamine synthesis. ceo_syn is related to the NAD-dependent L-alanine dehydrogenases. Like formate dehydrogenase and related enzymes, ceo_syn is comprised of 2 domains connected by a long alpha helical stretch, each resembling a Rossmann fold NAD-binding domain. The NAD-binding domain is inserted within the linear sequence of the more divergent catalytic domain. These ceo_syn proteins have a partially conserved NAD-binding motif and active site residues that are characteristic of related enzymes such as Saccharopine Dehydrogenase.
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