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|Section2= |Section6= |Section7= }} Xanthine ( or ; archaically xanthic acid) (3,7-dihydro-purine-2,6-dione), is a purine base found in most human body tissues and fluids and in other organisms. A number of stimulants are derived from xanthine, including caffeine and theobromine. Xanthine is a product on the pathway of purine degradation. * It is created from guanine by guanine deaminase. * It is created from hypoxanthine by xanthine oxidoreductase. * It is also created from xanthosine by purine nucleoside phosphorylase (PNP).〔Voet, Donald; Voet, Judith; Pratt, Charlotte (2008). "The Major Pathways of Purine Catabolism in Animals", ''Fundamentals of Biochemistry: Life at the Molecular Level'', p. 840.〕 Xanthine is subsequently converted to uric acid by the action of the xanthine oxidase enzyme. Studies reported in 2008, based on 12C/13C isotopic ratios of organic compounds found in the Murchison meteorite, suggested that xanthine and related chemicals, including the RNA component uracil, were formed extraterrestrially. In August 2011, a report, based on NASA studies with meteorites found on Earth, was published suggesting xanthine and related organic molecules, including the DNA and RNA components adenine and guanine, were made in outer space. ==Pathology== People with the rare genetic disorder xanthinuria lack sufficient xanthine oxidase and cannot convert xanthine to uric acid. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Xanthine」の詳細全文を読む スポンサード リンク
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