A research team delved into a small molecule, called 3-nitrooxypropanol, and the way it can inhibit methane emissions from ruminants when mixed into the feed.
By 2014, scientists had demonstrated the effectiveness of this molecule in sheep, but were unaware of how it actually worked. Now, in vivo research, using incubated anaerobic micro-organisms from ruminants' digestive systems have revealed how the compound 3-nitrooxypropanol only had an effect on methane producing micro-organisms (arqueas methanogens) and not on those which contribute to digestion (bacterias).
It was shown that 3-NOP specifically targets methyl-coenzyme M reductase (MCR). The nickel enzyme, which is only active when its Ni ion is in the +1 oxidation state, catalyzes the methane-forming step in the rumen fermentation. Molecular docking suggested that 3-NOP preferably binds into the active site of MCR in a pose that places its reducible nitrate group in electron transfer distance to Ni(I). With purified MCR, we found that 3-NOP indeed inactivates MCR at micromolar concentrations by oxidation of its active site Ni(I). Concomitantly, the nitrate ester is reduced to nitrite, which also inactivates MCR at micromolar concentrations by oxidation of Ni(I).
As David Yáñez, a CSIC researcher at the Zaidin Experimental Research Centre in Granada (southern Spain) explains, "Up until now, no-one had described the mode of action of a compound which can repeatedly reduce (by 30%) methane production in animals without any risks, either to the animal's health, or to their productivity." The results of this work open up the possibility of reducing methane emissions and contribute to a reduction in global temperatures which is caused by greenhouse gases.
The work has been published in the magazine, Proceedings of the National Academy of Sciences (PNAS).
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