Studies on chicken liver xanthine dehydrogenase with reference to the problem of non-equivalence of FAD moieties.
1. Reduction of chicken liver xanthine dehydrogenase (xanthine: NAD+ oxidoreductase, EC 1.2.1.37) by xanthine under anaerobic condition proceeded in two phases. This biphasicity may be due to functional and non-functional enzymes in the enzyme preparation. 2. Cyanolysis of a persulfide group of chicken liver enzyme resulted in an inactivation of the enzyme. The non-functional enzyme in the standard enzyme preparation was found to lack persulfide groups at the active sites. 3. The remaining NADH-Methylene Blue oxidoreductase activity, after KI treatment of the xanthine-reduced enzyme of a high flavin activity ratio, is not at the level of 50% of the initial activity, differing from the report suggesting non-equivalence of FAD chromophores. 4. The findings in the present report indicate that FAD chromophores of chicken liver enzyme are essentially equivalent.
D000818:Animals; D002645:Chickens; D003486:Cyanides / Q000494:pharmacology; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism*; D007454:Iodides / Q000494:pharmacology; D007658:Ketone Oxidoreductases / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D011485:Protein Binding; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D014968:Xanthine Dehydrogenase / Q000378:metabolism*
D003486:Cyanides; D007454:Iodides; D005182:Flavin-Adenine Dinucleotide; D014968:Xanthine Dehydrogenase; D007658:Ketone Oxidoreductases