Nitrite controls the release of nitric oxide in Pseudomonas aeruginosa cd₁ nitrite reductase

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• 作者：Serena Rinaldo ; Maurizio Brunori ; Francesca Cutruzzolà
• 关键词：Nitrite reductase ; Nitric oxide ; Pseudomonas aeruginosa ; d₁-heme ; Denitrification
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2007
• 期刊代码：159_0006291x
• 类别：bio
• 出版时间：23 November 2007
• 卷：363
• 期：3
• 页码：662-666
• 文件大小：206 K

摘要

Nitrite reductase (cd₁NIR) from Pseudomonas aeruginosa, which catalyses the reduction of nitrite to nitric oxide (NO), contains a c-heme as the electron acceptor and a d₁-heme where catalysis occurs. Reduction involves binding of nitrite to the reduced d₁-heme, followed by dehydration to yield NO; release of NO and re-reduction of the enzyme close the cycle. Since NO is a powerful inhibitor of ferrous hemeproteins, enzymatic turnover demands the release of NO. We recently discovered that NO dissociation from the ferrous d₁-heme is fast, showing that cd₁NIR behaves differently from other hemeproteins.

Here we demonstrate for the first time that the physiological substrate nitrite displaces NO from the ferrous enzyme, which enters a new catalytic cycle; this reaction depends on the conserved His369 whose role in substrate stabilization is crucial for catalysis. Thus we suggest that also in vivo the activity of cd₁NIR is controlled by nitrite.