ornithine /ôr″nithēn/ , an amino acid, not a constituent of proteins, that is produced as an important intermediate substance in the urea cycle. It is formed by the hydrolization of arginine by arginase and is subsequently converted into citrulline. It decomposes by losing carbon dioxide, producing putrescine and a strong foul odor characteristic of decaying animal tissue. Also called diaminovaleric acid.
