Respiratory nitrate reductase system

Sulfate reducers can use a wide range of terminal electron acceptors, and sulfate can be replaced by nitrate as a respiratory substrate. Molybdenum-containing enzymes have been discovered in SRB (also see later discussion) and, in particular, D. desulfuricans, grown in the presence of nitrate, generates a complex enzymatic system containing the following molybdenum enzymes (a) aldehyde oxidoreduc-tase (AOR), which reduces adehydes to carboxylic acids (b) formate dehydrogenase (FDH), which oxidizes formate to CO2 and (c) nitrate reductase (the first isolated from a SRB), which completes the enzy-... 

A wide variety of different cytochrome-linked electron-transfer systems is encountered in bacteria respiratory chains with oxygen, nitrate or sulphate as electron acceptors, fumarate reductase systems and light-driven cyclic electron-transfer systems (Fig. 3). All these systems are composed of several electron-transfer carriers, the nature of which varies considerably in different organisms. Electron carriers which are most common in bacterial electron-transfer systems are flavoproteins (dehydrogenases), quinones, non-heme iron centres, cytochromes and terminal oxidases and reductases. One common feature of all electron-transfer systems is that they are tightly incorporated in the cytoplasmic membrane. Another important general property of these systems is that electron transfer results in the translocation of protons from the cytoplasm into the external medium. Electron transfer therefore... 

Terminal oxidase the terminal enzyme of the respiratory chain. In most organisms it is Cytochrome oxidase (see), but in various plant systems other To. are present or have been proposed. In aerobic nitrate respiration, the T. o. is nitrate reductase. 

Proton-coupled electron transfer (PCET) is known to play an important role in a variety of biological processes, including microbial iron transport by ferric enterobactin, enzyme catalysis in systems such as fumarate reductase and nitrate reducatase, and dioxygen binding by the non-heme iron protein hemerythrin. " As such, pH-dependent electrochemical studies can play an important role in unraveling these mechanisms. The most heavily studied biological system known to involve PCET is cytochrome c oxidase, the terminal electron-transfer complex of the mitochondrial respiratory chain, which catalyzes the reduction of molecular oxygen to water. ... 

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