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Oxidation--reduction potentials of turkey liver xanthine dehydrogenase and the origins of oxidase and dehydrogenase behaviour in molybdenum-containing hydroxylases.
Biochem J. 1977 May 01; 163(2):279-89.BJ

Abstract

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.

Authors

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Pub Type(s)

Journal Article

Language

eng

PubMed ID

869927

Citation

Barber, M J., et al. "Oxidation--reduction Potentials of Turkey Liver Xanthine Dehydrogenase and the Origins of Oxidase and Dehydrogenase Behaviour in Molybdenum-containing Hydroxylases." The Biochemical Journal, vol. 163, no. 2, 1977, pp. 279-89.
Barber MJ, Bray RC, Cammack R, et al. Oxidation--reduction potentials of turkey liver xanthine dehydrogenase and the origins of oxidase and dehydrogenase behaviour in molybdenum-containing hydroxylases. Biochem J. 1977;163(2):279-89.
Barber, M. J., Bray, R. C., Cammack, R., & Coughlan, M. P. (1977). Oxidation--reduction potentials of turkey liver xanthine dehydrogenase and the origins of oxidase and dehydrogenase behaviour in molybdenum-containing hydroxylases. The Biochemical Journal, 163(2), 279-89.
Barber MJ, et al. Oxidation--reduction Potentials of Turkey Liver Xanthine Dehydrogenase and the Origins of Oxidase and Dehydrogenase Behaviour in Molybdenum-containing Hydroxylases. Biochem J. 1977 May 1;163(2):279-89. PubMed PMID: 869927.
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TY - JOUR T1 - Oxidation--reduction potentials of turkey liver xanthine dehydrogenase and the origins of oxidase and dehydrogenase behaviour in molybdenum-containing hydroxylases. AU - Barber,M J, AU - Bray,R C, AU - Cammack,R, AU - Coughlan,M P, PY - 1977/5/1/pubmed PY - 1977/5/1/medline PY - 1977/5/1/entrez SP - 279 EP - 89 JF - The Biochemical journal JO - Biochem J VL - 163 IS - 2 N2 - 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. SN - 0264-6021 UR - https://www.unboundmedicine.com/medline/citation/869927/Oxidation__reduction_potentials_of_turkey_liver_xanthine_dehydrogenase_and_the_origins_of_oxidase_and_dehydrogenase_behaviour_in_molybdenum_containing_hydroxylases_ L2 - https://portlandpress.com/biochemj/article-lookup/doi/10.1042/bj1630279 DB - PRIME DP - Unbound Medicine ER -