Nitrate ester reductase

A group of flavoenzyme reductases mediate the reduction both nitrate esters and C= C double bonds generally activated with carbonyl or nitro functions. The structures of the substrates vary widely (references in Faber 1997). 

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All bacteria where nitrate ester degradation has been characterized have very similar enzymes. The enzymes eatalyze the nicotinamide cofactor-dependent reductive eleavage of nitrate esters that produces alcohol and nitrite. Purification of the PETN reduetase from Enterobacter cloacae yielded a monomerie protein of around 40 kilo Daltons, which required NADPH as a co-faetor for aetivity. Similar enzymes were responsible for the nitrate ester-degrading activity in Agrobacterium radiobacter (Snape et al. 1997) - nitrate ester reductase - and in the strains of Pseudomonas fluorescens and Pseudomonas putida (Blehert et al. 1999) - xenobiotic reduetases . All utilize a non-covalently bound flavine mononucleotide as a redox eofactor. 

When the nitrate ester 277 was treated with BuaSnD and AIBN, the deuteriated alcohol 278 was formed, by 1,5-radical translocation. However, the 2 -chloro-2 -deoxy-system 279 gave the furanone 280 under the same conditions. These results suggest that the inhibition of ribonucleoside diphosphate reductase by 2 -chloro-2 -deoxynucleosides involves loss of Cl from a radical at C-3. Some related studies from the same team, also supporting this conclusion, were mentioned earlier. ... 

The recognition that the Mo in the molybdoproteins exists in organic cofactor forms came from studies of mutants of Aspergillus and Neurospora.650 In 1964, Pateman and associates discovered mutants that lacked both nitrate reductase and xanthine dehydrogenase. Later, it was shown that acid-treated molybdoenzymes released a material that would restore activity to the inactived nitrate reductase from the mutant organisms. This new coenzyme, a phosphate ester of molybdopterin (Fig. 15-17), was characterized by Rajagopalan and coworkers.650 651 A more complex form of the coenzyme, molybdopterin cytosine dinucleotide... 

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