Cytochrome b5 reductase is an enzyme with the ability to generate superoxide anion at the expenses of NADH consumption. Although this activity can be stimulated by cytochrome c and could participate in the bioenergetic failure accounting in apoptosis, very little is known about other molecules that may uncouple the function of the cytochrome b5 reductase. Naphthoquinones are redox active molecules with the ability to interact with electron transfer chains. In this work, we made an inhibitor screening against recombinant human cytochrome b5 reductase based on naphthoquinone properties. We found that 5-hydroxy-1,4-naphthoquinone (known as juglone), a natural naphthoquinone extracted from walnut trees and used historically in traditional medicine with ambiguous health and toxic outcomes, had the ability to uncouple the electron transfer from the reductase to cytochrome b5 and ferricyanide. Upon complex formation with cytochrome b5 reductase, juglone is able to act as an electron acceptor leading to a NADH consumption stimulation and an increase of superoxide anion production by the reductase. Our results suggest that cytochrome b5 reductase could contribute to the measured energetic failure in the erythrocyte apoptosis induced by juglone, that is concomitant with the reactive oxygen species produced by cytochrome b5 reductase.

中文翻译：

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人红细胞暴露于juglone会导致与细胞色素b5还原酶解偶联相关的超氧阴离子产生增加。

细胞色素b5还原酶是一种能够以消耗NADH为代价生成超氧阴离子的酶。尽管这种活性可以被细胞色素c刺激，并可能参与细胞凋亡中的生物能衰竭，但对其他可能解开细胞色素b5还原酶功能的分子知之甚少。萘醌是具有与电子转移链相互作用的能力的氧化还原活性分子。在这项工作中，我们根据萘醌特性对重组人细胞色素b5还原酶进行了抑制剂筛选。我们发现5-羟基-1,4-萘醌（被称为juglone）是一种从核桃树中提取的天然萘醌，历史上曾在传统医学中使用，对健康和毒性都有不确定性，具有解耦电子从还原酶转移至细胞色素b5和铁氰化物的能力。与细胞色素b5还原酶形成复合物后，胡胶可以充当电子受体，从而刺激NADH消耗并通过还原酶增加超氧阴离子的产生。我们的结果表明，细胞色素b5还原酶可能有助于测定由朱古力诱导的红细胞凋亡中的能量衰竭，这与细胞色素b5还原酶产生的活性氧物种同时存在。