Xanthines are a group of alkaloids that are commonly used for their effects as mild stimulants and as bronchodilators, notably in treating the symptoms of asthma. They include caffeine, theophylline, theobromine (found mainly in chocolate), and mateine. Xanthine, also known as dioxopurine is a a precursor of uric acid and is found in blood and urine, muscle tissue and in certain plants. It is a toxic yellowish white powder insoluble in water and acids but soluble in caustic soda; sublimes when heated. It is involved in purine degradation and is converted to uric acid by xanthine oxidase. Purine is a heterocyclic compound featured by a fused pyrimidine and imidazole rings composed of carbon and nitrogen atoms. The simplest one is purine itself and the two major purines are adenine (6-Aminopurine) and guanine (2-Amino-6-hydroxypurine). Other important purines are caffeine, uric acid, theobromine, and theophylline. Purine and its derivatives are biologically important components of nucleic acids (DNA, RNA) and coenzymes. Xanthine and its derivatives are used in medicine as a chemical intermediate.
The core compound, xanthine, is a product on the pathway of purine degradation and is converted to uric acid by the action of xanthine oxidase. Xanthine is a two-oxygen cousin of adenine and guanine, the purine bases of DNA. Uric acid is a three-oxygen cousin, and methlyated relatives include key ingredients in coffee and chocolate: caffeine and, theobromine. Xanthine combined with its isomer oxypurinol forms an anti-cockroach pesticide that doesn't harm humans.
Xanthine oxidase is a molybdenum-utilizing enzyme which exists predominantly as a dehydrogenase which utilizes NAD+ as the electron acceptor, but can be converted to an oxidase which utilizes molecular oxygen as the electron acceptor. In rats (and in some lower eukaryotes, such as D. melanogaster), xanthine oxidase has been demonstrated to be both cytoplasmic and peroxisomal by immunocytochemistry (Angermuller et al). In addition, the rat enzyme terminates in a loose consensus to the PTS1, Val-Arg-Ile. However, the human enzyme does not contain this terminal tripeptide, and has never been demonstrated to be peroxisomal.
CAS NO. 69-89-6
Molecular formula: C5H4N4O2
Molecular weight: 152.11
Synonyms: 2,6-Dioxopurine; 2,6-Dioxypurine; 3,7-dihydro-1H-Purine-2,6-dione, ; X; Xan; Xanthic oxide