Definition of ornithine in US English:



  • An amino acid which is produced by the body and is important in protein metabolism.

    Chemical formula: NH₂(CH₂)₃CH(NH₂)COOH

    • ‘The trial was investigating a treatment for a genetic liver condition, where a gene for a liver enzyme, ornithine trans-carbamylase, is either missing or defective.’
    • ‘He was undergoing treatment for ornithine transcarbamylase deficiency, a disorder that prevents the liver from effectively processing ammonia, a toxin produced in the breakdown of proteins.’
    • ‘About 50-percent of ingested arginine is rapidly converted in the body to ornithine, primarily by the enzyme arginase.’
    • ‘When your body doesn't digest protein completely, gut bacteria convert two of the amino acids in protein, arginine and ornithine, to compounds called polyamines.’
    • ‘This may occur in part as a result of pathologically elevated activity of arginase, an enzyme that hydrolyzes arginine to ornithine and urea.’


Late 19th century: from ornitho- (with reference to a constituent found in bird excrement) + -ine.