Reduction and Condensation of Aldehydes by the Isolated Cofactor of Nitrogenase

Abstract

Isolated nitrogenase cofactors can reduce CO, CN–, and CO2 to short-chain hydrocarbons in reactions driven by a strong reductant. Here, we use activity analyses and isotope labeling experiments to show that formaldehyde and acetaldehydes can be reduced as-is or reductively condensed into alkanes and alkenes by the isolated cofactor of Mo-nitrogenase in the presence of EuII-diethylenetriamine pentaacetate (DTPA). Further, we demonstrate that aldehydes can be condensed with CO by the isolated cofactor under the same reaction conditions, pointing to aldehyde-derived species as possible intermediates of nitrogenase-catalyzed CO reduction. Our deuterium labeling experiments suggest the formation of a cofactor-bound hydroxymethyl intermediate upon activation of the formaldehyde, as well as the release of C2H4 as a product upon β-hydride elimination of an acetaldehyde-derived hydroxyethyl intermediate. These findings establish the reductive condensation of aldehydes as a previously unobserved reactivity of a biogenic catalyst while at the same time shed light on the mechanism of enzymatic CO reduction and C–C bond formation, thereby providing a useful framework for further exploration of the unique reactivity and potential applications of nitrogenase-based reactions.

Photo-driven CO2 Reduction to Hydrocarbons: Carbon Flux and Energy Transforming by Marine Microbial Community

“…Particularly, Mo nitrogenase and Fe-only nitrogenase accounted for more than 50% of all types in all samples (Fig. 5b), which were currently well-reported the performance on catalyzing the reduction of C 1 substrates including CO and CO 2 to hydrocarbons [43][44][45]. According to metagenomic analysis, Shigella (bin 6), Candidatus (bin 7), Clostridium (bin 8), Azospirillum (bin 9), Azotobacter (bin 10), Vibrio (bin 11), Rhodospirillum (bin 15), Pseudomonas (bin 16), Desulfovibrio (bin 18), and Deinococcus (bin 19), were dominantly observed in all samples (Fig.…”

“…According to metagenomic analysis, Shigella (bin 6), Candidatus (bin 7), Clostridium (bin 8), Azospirillum (bin 9), Azotobacter (bin 10), Vibrio (bin 11), Rhodospirillum (bin 15), Pseudomonas (bin 16), Desulfovibrio (bin 18), and Deinococcus (bin 19), were dominantly observed in all samples (Fig. S9), which were capable of secreting nitrogenase especially Mo and Fe-only types under aerobic or anaerobic conditions [18,22,[43][44][45]. Furthermore, the abundance of the facultative and obligate anaerobic microbes, like Clostridium, Pseudomonas and Desulfovibrio, were increasingly detected along with depletion of oxygen (Fig.…”

“…Recent researches and developments in biofuels have revealed an assortment of enzymes that can catalyze fatty acids, alcohol, or aldehyde to hydrocarbons [21,25,27,29,[43][44][45], and particularly elaborated the signi cant role of carboxylic acid reductase (CARs), aldehyde decarbonylase, and nitrogenase in the production of alkane or alkene [20,29,30,46]. Generally, the activity of AD from microbes is oxygen-dependently triggered.…”

“…Nitrogenases, including three homologous nitrogenase enzymes that documented as the Mo nitrogenase, V nitrogenase and Fe-only nitrogenase, were extensively reported to convert small molecules (such as cyanide ions, carbon monoxide, acetate, butanol, butyrate, cyclohexane carboxylate, ethanol, fumarate, succinate, formaldehyde or acetaldehydes) with reductant to alkanes and alkenes under ambient conditions [18,27,[43][44][45]. In our study, nitrogen was consumed with rapid decreasing rate at 200.88 uM day -1 from 15859.38 uM to 12444.43 uM before 17 th day (Fig.…”

“…S9). Pseudomonas (bin 16), Rhodospirillum (bin 15), Rhodopseudomonas (bin 20), Rhodobacter (bin 21), Dickeya (bin 22) and Enterococcus (bin 23), belong to the phylum of Proteobacteria, had the intrinsic property of expressing the Fe-only nitrogenases to produce an amount of CH 4 and NH 3 with light and CO 2 and N 2 [18,[43][44][45] This evidence con rmed the conspicuous phenomenon of CH 4 production and N 2 xation at the beginning of culturing when oxygen was in the presence. Other phototrophic bacteria, Rhodospirillum and Rhodobacter, and Azotobacter were detected, and each can produce CH 4 when grown with N 2 as a sole nitrogen source under Fe-only nitrogenase expressing condition [18,[43][44][45]48].…”