title: [Functional groups involved in the nitrate reductase activity of milk xanthine oxidase].
abstract: Milk xanthine oxidase possesses the nitrate reductase activity at pH 5.2; the pH optimum of the xanthine oxidase activity for the enzyme lies at 9.6. After removal of FAD and binding of Mo and Fe with a simultaneous measurement at the pH optima of the above activities it was found that only the Mo-containing site is necessary for the nitrate reductase activity. The switch-over of the enzyme from the xanthine oxidase to the nitrate reductase activity is associated with considerable conformational changes of the enzyme molecule.
mesh_terms: D000818:Animals; D002417:Cattle; D005260:Female; D005182:Flavin-Adenine Dinucleotide / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008892:Milk / Q000201:enzymology*; D009565:Nitrate Reductases / Q000378:metabolism*; D013053:Spectrophotometry; D014969:Xanthine Oxidase / Q000378:metabolism*
chemical_list: D005182:Flavin-Adenine Dinucleotide; D014969:Xanthine Oxidase; D009565:Nitrate Reductases
vernacular_title: Issledovanie funktsional'nykh grupp, uchastvuiushchikh v nitratreduktaznoĭ aktivnosti ksantinoksidazy moloka.