真菌异化硝酸盐还原机理的研究进展

真菌异化硝酸盐还原途径的发现打破了反硝化仅存在于原核细胞这一传统观念。真菌异化硝酸盐还原途径是在环境中氧供给受限的情况下发生的, 包括反硝化和氨的发酵。硝酸盐能诱导产生反硝化作用的酶, 其中, 硝酸盐还原酶与亚硝酸还原酶位于线粒体中, 它们所催化的酶促反应能偶联呼吸链ATP合成酶合成ATP, 同时产生NO。与参与反硝化作用前两个酶不同, 真菌NO还原酶能以NADH为直接电子供体将NO还原为N2O, 在NAD+的再生和自由基NO的脱毒中起着重要作用。氨发酵则将硝酸盐还原成NH4+, 同时偶联乙酸的生成和底物水平磷酸化。此文从参与该过程的关键酶、关键酶的表达调节、真菌与细菌异化硝酸盐还原的比较等角度综述了真菌异化硝酸盐还原的最新研究进展。

Study Progress on the Mechanism of Dissimilatory Nitrate Reduction in Fungi

The finding of dissimilatory nitrate reductase in fungi breaks the traditional concept that denitrification has been considered to only occur in a prokaryotic cell. Dissimilatory nitrate reduction in fungi includes denitrification and ammonia fermentation, which occurs under the conditions of limited aeration. Nitrate and nitrite can induce denitrification-related enzymes, which include nitrate reductase, nitrite reductase and nitric oxide reductase. Nitrate reductase and nitrite reductase exists in mitochondria, and enzymatic reactions they catalyze are coupled with ATP generation through ATP synthase in the respiratory chain and produce nitric oxide(NO). In contrast to the two enzymes, NO reductase uses NADH as the direct electron donor and thus might function in the regeneration of NAD+ and detoxification of the toxic radical, NO. Ammonia fermentation can reduce nitrate to ammonium and couples acetogenic reaction with substrate-level phosphorylation. In this review, the latest progress about the involved main enzymes, their gene expression regulation, and the comparison of the dissimilatory nitrate reduction between fungi and bacteria were discussed.