Maesaquinone: A Novel Inhibitor of Plant Mitochondrial Respiratory Enzymes That React with Ubiquinone

The alternative oxidase (AOX) is a ubiquitous terminal oxidase of plants and many fungi, catalyzing the four‐electron reduction of oxygen to water alongside the cytochrome‐based electron transfer chain. Unlike the classical electron transfer chain, however, the activity of AOX does not generate adenosine triphosphate but has functions such as thermogenesis and stress response. As it lacks a mammalian counterpart, it has been investigated intensely in pathogenic fungi. However, it is in African trypanosomes, which lack cytochrome‐based respiration in their infective stages, that trypanosome alternative oxidase (TAO) plays the central and essential role in their energy metabolism. TAO was validated as a drug target decades ago and among the first inhibitors to be identified was salicylhydroxamic acid (SHAM), which produced the expected trypanocidal effects, especially when potentiated by coadministration with glycerol to inhibit anaerobic energy metabolism as well. However, the efficacy of this combination was too low to be of practical clinical use. The antibiotic ascofuranone (AF) proved a much stronger TAO inhibitor and was able to cure Trypanosoma vivax infections in mice without glycerol and at much lower doses, providing an important proof of concept milestone. Systematic efforts to improve the SHAM and AF scaffolds, aided with the elucidation of the TAO crystal structure, provided detailed structure‐activity relationship information and reinvigorated the drug discovery effort. Recently, the coupling of mitochondrion‐targeting lipophilic cations to TAO inhibitors has dramatically improved drug targeting and trypanocidal activity while retaining target protein potency. These developments appear to have finally signposted the way to preclinical development of TAO inhibitors.

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Alternative oxidase inhibitors: Mitochondrion‐targeting as a strategy for new drugs against pathogenic parasites and fungi

Ebiloma

Balogun

Cueto-Díaz

et al. 2019

Medicinal Research Reviews

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Cyanide-resistant respiration, a very frequent metabolic pathway in yeasts

Veiga¹,

Arrabaça²,

Loureiro-Dias³

2003

FEMS Yeast Research

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It has recently been shown that cyanide-resistant respiration (CRR) is very common in Crabtree-negative yeasts (incapable of aerobic fermentation) and in non-fermentative yeasts. It is conferred by a salicylhydroxamic acid-sensitive alternative oxidase that transfers electrons from ubiquinol to oxygen, bypassing the cytochrome chain. An interesting finding is that, in general, whenever CRR is present, complex I is also present. In this article we briefly review the occurrence of CRR, the biochemistry and molecular biology of the alternative oxidase, and summarise the putative functions that have been attributed to this ubiquitous metabolic pathway, whose usefulness for the yeast cells still remains obscure.

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Maesaquinone: A Novel Inhibitor of Plant Mitochondrial Respiratory Enzymes That React with Ubiquinone

Cited by 2 publications

References 29 publications

Alternative oxidase inhibitors: Mitochondrion‐targeting as a strategy for new drugs against pathogenic parasites and fungi

Alternative oxidase inhibitors: Mitochondrion‐targeting as a strategy for new drugs against pathogenic parasites and fungi

Cyanide-resistant respiration, a very frequent metabolic pathway in yeasts

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