xanthine(redirected from xanthine calculi)
Also found in: Dictionary, Thesaurus, Encyclopedia.
Oxidation product of guanine and hypoxanthine, precursor of uric acid; occurs in many organs and in the urine, occasionally forming urinary calculi; elevated in molybdenum cofactor deficiency and in xanthinuria.
xanthine/xan·thine/ (-thēn) a purine base found in most body tissues and fluids, certain plants, and some urinary calculi; it is an intermediate in the degradation of AMP to uric acid. Methylated xanthine compounds (e.g., caffeine, theobromine, theophylline) are used for their bronchodilator effect. Abbreviated X.
1. A yellowish-white, crystalline purine base, C5H4N4O2, that is a precursor of uric acid and is found in blood, urine, muscle tissue, and certain plants.
2. Any of several derivatives of this compound.
Etymology: Gk, xanthos, yellow
a nitrogenous by-product of the metabolism of nucleoproteins. It is normally found in the muscles, liver, spleen, pancreas, and urine. xanthic, adj.
Oxidation product of guanine and hypoxanthine, precursor of uric acid; occurs in many organs and in the urine, occasionally forming urinary calculi.
a purine compound found in most bodily tissues and fluids; it is a precursor of uric acid. Xanthine compounds such as theophylline have diuretic properties.
see xanthine urolith.
key enzyme in the pathway for purine breakdown. Catalyzes the conversion of hypoxanthine to xanthine and then to uric acid. Generates hydrogen peroxide, which can be a generator of free radicals in biological systems through reactions with superoxide ions.