Direct electrochemistry of nitrate reductase from the fungus Neurospora crassa

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• 作者：Palraj Kalimuthu^a ; Phillip Ringel^b ; Tobias Kruse^b ; Paul V. Bernhardt^a ; ^{p.bernhardt@uq.edu.au" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Molybdenum ; Enzyme ; Voltammetry ; Nitrate reductase
• 刊名：Biochimica et Biophysica Acta (BBA) - Bioenergetics
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：1857
• 期：9
• 页码：1506-1513
• 全文大小：1419 K

文摘

We report the first direct (unmediated) catalytic electrochemistry of a eukaryotic nitrate reductase (NR). NR from the filamentous fungus Neurospora crassa, is a member of the mononuclear molybdenum enzyme family and contains a Mo, heme and FAD cofactor which are involved in electron transfer from NAD(P)H to the (Mo) active site where reduction of nitrate to nitrite takes place. NR was adsorbed on an edge plane pyrolytic graphite (EPG) working electrode. Non-turnover redox responses were observed in the absence of nitrate from holo NR and three variants lacking the FAD, heme or Mo cofactor. The FAD response is due to dissociated cofactor in all cases. In the presence of nitrate, NR shows a pronounced cathodic catalytic wave with an apparent Michaelis constant (K_M) of 39 μM (pH 7). The catalytic cathodic current increases with temperature from 5 to 35 °C and an activation enthalpy of 26 kJ mol^− 1 was determined. In spite of dissociation of the FAD cofactor, catalytically activity is maintained.