BIOMAT Database Logo BIOMAT Database Logo

Oxidation--reduction potentials of turkey liver xanthine dehydrogenase and the origins of oxidase and dehydrogenase behaviour in molybdenum-containing hydroxylases. 1977

M J Barber, and R C Bray, and R Cammack, and M P Coughlan

Redox potentials for the various centres in the enzyme xanthine dehydrogenase (EC 1.2.1.37) from turkey liver determined by potentiometric titration in the presence of mediator dyes, with low-temperature electron-paramagnetic-resonance spectroscopy. Values at 25 degrees C in pyrophosphate buffer, pH 8.2, are: Mo(VI)/Mo(V)(Rapid),-350 +/- 20mV; Mo(V) (Rapid)/Mo(IV), -362 +/- 20mV; Fe-S Iox./Fe-S Ired., -295 +/- 15mV; Fe-S IIox./Fe-S IIred., -292 +/- 15mV; FAD/FADH,-359+-20mV; FADH/FADH2, -366 +/- 20mV. This value of the FADH/FADH2 potential, which is 130mV lower than the corresponding one for milk xanthine oxidase [Cammack, Barber & Bray (1976) Biochem. J. 157, 469-478], accounts for many of the differences between the two enzymes. When allowance is made for some interference by desulpho enzyme, then differences in the enzymes' behaviour in titration with xanthine [Barber, Bray, Lowe & Coughlan (1976) Biochem. J. 153, 297-307] are accounted for by the potentials. Increases in the molybdenum potentials of the enzymes caused by the binding of uric acid are discussed. Though the potential of uric acid/xanthine (-440mV) is favourable for full reduction of the dehydrogenase, nevertheless, during turnover, for kinetic reasons, only FADH and very little FADH2 is produced from it. Since only FADH2 is expected to react with O2, lack of oxidase activity by the dehydrogenase is explained. Reactivity of the two enzymes with NAD+ as electron acceptor is discussed in relation to the potentials.

UI MeSH Term Description Entries
D007658 Ketone Oxidoreductases Oxidoreductases that are specific for KETONES. Oxidoreductases, Ketone
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D008982 Molybdenum A metallic element with the atomic symbol Mo, atomic number 42, and atomic weight 95.95. It is an essential trace element, being a component of the enzymes xanthine oxidase, aldehyde oxidase, and nitrate reductase. Molybdenum-98,Molybdenum 98
D010084 Oxidation-Reduction A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471). Redox,Oxidation Reduction
D005182 Flavin-Adenine Dinucleotide A condensation product of riboflavin and adenosine diphosphate. The coenzyme of various aerobic dehydrogenases, e.g., D-amino acid oxidase and L-amino acid oxidase. (Lehninger, Principles of Biochemistry, 1982, p972) FAD,Flavitan,Dinucleotide, Flavin-Adenine,Flavin Adenine Dinucleotide
D006899 Mixed Function Oxygenases Widely distributed enzymes that carry out oxidation-reduction reactions in which one atom of the oxygen molecule is incorporated into the organic substrate; the other oxygen atom is reduced and combined with hydrogen ions to form water. They are also known as monooxygenases or hydroxylases. These reactions require two substrates as reductants for each of the two oxygen atoms. There are different classes of monooxygenases depending on the type of hydrogen-providing cosubstrate (COENZYMES) required in the mixed-function oxidation. Hydroxylase,Hydroxylases,Mixed Function Oxidase,Mixed Function Oxygenase,Monooxygenase,Monooxygenases,Mixed Function Oxidases,Function Oxidase, Mixed,Function Oxygenase, Mixed,Oxidase, Mixed Function,Oxidases, Mixed Function,Oxygenase, Mixed Function,Oxygenases, Mixed Function
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D014422 Turkeys Large woodland game BIRDS in the subfamily Meleagridinae, family Phasianidae, order GALLIFORMES. Formerly they were considered a distinct family, Melegrididae. Meleagridinae,Meleagrididae
D014968 Xanthine Dehydrogenase An enzyme that catalyzes the oxidation of XANTHINE in the presence of NAD+ to form URIC ACID and NADH. It acts also on a variety of other purines and aldehydes. Purine Hydroxylase I,Xanthine Oxidoreductase,Dehydrogenase, Xanthine,Oxidoreductase, Xanthine
D014969 Xanthine Oxidase An iron-molybdenum flavoprotein containing FLAVIN-ADENINE DINUCLEOTIDE that oxidizes hypoxanthine, some other purines and pterins, and aldehydes. Deficiency of the enzyme, an autosomal recessive trait, causes xanthinuria. Hypoxanthine Oxidase,Hypoxanthine Dehydrogenase,Hypoxanthine-Xanthine Oxidase,Purine-Xanthine Oxidase,Dehydrogenase, Hypoxanthine,Hypoxanthine Xanthine Oxidase,Oxidase, Hypoxanthine,Oxidase, Hypoxanthine-Xanthine,Oxidase, Purine-Xanthine,Oxidase, Xanthine,Purine Xanthine Oxidase

Related Publications

M J Barber, and R C Bray, and R Cammack, and M P Coughlan
Molybdenum hydroxylases in Drosophila. II. Molybdenum cofactor in xanthine dehydrogenase, aldehyde oxidase and pyridoxal oxidase.
January 1981, Molecular & general genetics : MGG,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
Electron paramagnetic resonance properties and oxidation-reduction potentials of the molybdenum, flavin, and iron-sulfur centers of chicken liver xanthine dehydrogenase.
May 1980, Archives of biochemistry and biophysics,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
Oxidation-reduction potentials of molybdenum, flavin, and iron-sulfur centers in milk xanthine oxidase: variation with pH.
March 1982, Biochemistry,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
Molybdenum hydroxylases in Drosophila. III. Further characterization of the low xanthine dehydrogenase gene.
August 1986, Biochemical genetics,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
Tissue distribution of the molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase, in male and female guinea pigs.
January 1987, European journal of drug metabolism and pharmacokinetics,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
[Comparative study of chicken liver xanthine dehydrogenase and bovine liver xanthine oxidase. dehydrogenase activity of xanthine oxidase (author's transl)].
March 1979, Revista espanola de fisiologia,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
The oxidation product of molybdenum cofactor from milk xanthine oxidase.
July 1987, Biochemistry international,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
On the mechanism of action of xanthine oxidase. Evidence in support of an oxo transfer mechanism in the molybdenum-containing hydroxylases.
August 1987, The Journal of biological chemistry,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
Electron paramagnetic resonance and potentiometric studies of arsenite interaction with the molybdenum centers of xanthine oxidase, xanthine dehydrogenase, and aldehyde oxidase: a specific stabilization of the molybdenum(V) oxidation state.
February 1983, Biochemistry,
M J Barber, and R C Bray, and R Cammack, and M P Coughlan
Equilibrium properties of xanthine oxidase containing FAD analogs of varying oxidation-reduction potential.
September 1981, The Journal of biological chemistry,
Copied contents to your clipboard!