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Nitrite reductase activity of rat and human xanthine oxidase, xanthine dehydrogenase, and aldehyde oxidase: evaluation of their contribution to NO formation in vivo.
Biochemistry. 2015 Jan 27; 54(3):685-710.B

Abstract

Nitrite is presently considered a NO "storage form" that can be made available, through its one-electron reduction, to maintain NO formation under hypoxia/anoxia. The molybdoenzymes xanthine oxidase/dehydrogenase (XO/XD) and aldehyde oxidase (AO) are two of the most promising mammalian nitrite reductases, and in this work, we characterized NO formation by rat and human XO/XD and AO. This is the first characterization of human enzymes, and our results support the employment of rat liver enzymes as suitable models of the human counterparts. A comprehensive kinetic characterization of the effect of pH on XO and AO-catalyzed nitrite reduction showed that the enzyme's specificity constant for nitrite increase 8-fold, while the Km(NO2(-)) decrease 6-fold, when the pH decreases from 7.4 to 6.3. These results demonstrate that the ability of XO/AO to trigger NO formation would be greatly enhanced under the acidic conditions characteristic of ischemia. The dioxygen inhibition was quantified, and the Ki(O2) values found (24.3-48.8 μM) suggest that in vivo NO formation would be fine-tuned by dioxygen availability. The potential in vivo relative physiological relevance of XO/XD/AO-dependent pathways of NO formation was evaluated using HepG2 and HMEC cell lines subjected to hypoxia. NO formation by the cells was found to be pH-, nitrite-, and dioxygen-dependent, and the relative contribution of XO/XD plus AO was found to be as high as 50%. Collectively, our results supported the possibility that XO/XD and AO can contribute to NO generation under hypoxia inside a living human cell. Furthermore, the molecular mechanism of XO/AO-catalyzed nitrite reduction was revised.

Authors+Show Affiliations

UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa , 2829-516 Caparica, Portugal.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

25537183

Citation

Maia, Luisa B., et al. "Nitrite Reductase Activity of Rat and Human Xanthine Oxidase, Xanthine Dehydrogenase, and Aldehyde Oxidase: Evaluation of Their Contribution to NO Formation in Vivo." Biochemistry, vol. 54, no. 3, 2015, pp. 685-710.
Maia LB, Pereira V, Mira L, et al. Nitrite reductase activity of rat and human xanthine oxidase, xanthine dehydrogenase, and aldehyde oxidase: evaluation of their contribution to NO formation in vivo. Biochemistry. 2015;54(3):685-710.
Maia, L. B., Pereira, V., Mira, L., & Moura, J. J. (2015). Nitrite reductase activity of rat and human xanthine oxidase, xanthine dehydrogenase, and aldehyde oxidase: evaluation of their contribution to NO formation in vivo. Biochemistry, 54(3), 685-710. https://doi.org/10.1021/bi500987w
Maia LB, et al. Nitrite Reductase Activity of Rat and Human Xanthine Oxidase, Xanthine Dehydrogenase, and Aldehyde Oxidase: Evaluation of Their Contribution to NO Formation in Vivo. Biochemistry. 2015 Jan 27;54(3):685-710. PubMed PMID: 25537183.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Nitrite reductase activity of rat and human xanthine oxidase, xanthine dehydrogenase, and aldehyde oxidase: evaluation of their contribution to NO formation in vivo. AU - Maia,Luisa B, AU - Pereira,Vânia, AU - Mira,Lurdes, AU - Moura,José J G, Y1 - 2015/01/08/ PY - 2014/12/25/entrez PY - 2014/12/30/pubmed PY - 2015/4/15/medline SP - 685 EP - 710 JF - Biochemistry JO - Biochemistry VL - 54 IS - 3 N2 - Nitrite is presently considered a NO "storage form" that can be made available, through its one-electron reduction, to maintain NO formation under hypoxia/anoxia. The molybdoenzymes xanthine oxidase/dehydrogenase (XO/XD) and aldehyde oxidase (AO) are two of the most promising mammalian nitrite reductases, and in this work, we characterized NO formation by rat and human XO/XD and AO. This is the first characterization of human enzymes, and our results support the employment of rat liver enzymes as suitable models of the human counterparts. A comprehensive kinetic characterization of the effect of pH on XO and AO-catalyzed nitrite reduction showed that the enzyme's specificity constant for nitrite increase 8-fold, while the Km(NO2(-)) decrease 6-fold, when the pH decreases from 7.4 to 6.3. These results demonstrate that the ability of XO/AO to trigger NO formation would be greatly enhanced under the acidic conditions characteristic of ischemia. The dioxygen inhibition was quantified, and the Ki(O2) values found (24.3-48.8 μM) suggest that in vivo NO formation would be fine-tuned by dioxygen availability. The potential in vivo relative physiological relevance of XO/XD/AO-dependent pathways of NO formation was evaluated using HepG2 and HMEC cell lines subjected to hypoxia. NO formation by the cells was found to be pH-, nitrite-, and dioxygen-dependent, and the relative contribution of XO/XD plus AO was found to be as high as 50%. Collectively, our results supported the possibility that XO/XD and AO can contribute to NO generation under hypoxia inside a living human cell. Furthermore, the molecular mechanism of XO/AO-catalyzed nitrite reduction was revised. SN - 1520-4995 UR - https://www.unboundmedicine.com/medline/citation/25537183/Nitrite_reductase_activity_of_rat_and_human_xanthine_oxidase_xanthine_dehydrogenase_and_aldehyde_oxidase:_evaluation_of_their_contribution_to_NO_formation_in_vivo_ L2 - https://doi.org/10.1021/bi500987w DB - PRIME DP - Unbound Medicine ER -