title: Formation of thieno[3,2-g]pterines from the molybdenum cofactor.
abstract: A fluorescent oxidation product of the molybdenum cofactor was isolated from Escherichia coli nitrate reductase (EC 1.9.6.1) and bovine milk xanthine oxidase (EC 1.2.3.2), which showed a visible absorption band at 395 nm and was dephosphorylated by alkaline phosphatase but not by phosphodiesterase I. The dephosphorylated species was oxidized by periodate to thieno[3,2-g]pterin-2-carbaldehyde which was quantitatively converted to thieno[3,2-g]pterin-2-carboxylic acid by subsequent treatment with Ag2O in 2 N NaOH. These results indicate that the oxidation product of the molybdenum cofactor is a thieno[3,2-g]pterin derivative with an unidentified side chain in the 2 position.
mesh_terms: D000818:Animals; D002417:Cattle; D003067:Coenzymes; D004926:Escherichia coli / Q000201:enzymology; D008667:Metalloproteins; D008982:Molybdenum / Q000378:metabolism*; D000090006:Molybdenum Cofactors; D009565:Nitrate Reductases / Q000378:metabolism; D011621:Pteridines / Q000378:metabolism*; D011622:Pterins / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D014969:Xanthine Oxidase / Q000378:metabolism
chemical_list: D003067:Coenzymes; D008667:Metalloproteins; D008982:Molybdenum; D000090006:Molybdenum Cofactors; D009565:Nitrate Reductases; D011621:Pteridines; D011622:Pterins; D014969:Xanthine Oxidase; C022261:molybdopterin