Remodeled enzyme converts carbon dioxide into methane

A nitrogenase is a single complex comprised of several protein subunits.

MIT.edu

An engineered enzyme is the first single biological catalyst that converts carbon dioxide into a renewable form of energy: methane. Surprisingly, the same enzyme can use carbon dioxide to make an important ingredient in plastics as well.

Recycling carbon dioxide by turning it into fuels like methanol (CH₃OH) or methane (CH₄) might be one way to slow the CO₂ accumulation in our atmosphere. But that's quite a challenge, because CO₂ is a pretty inert molecule and doesn't readily participate in chemical reactions. So chemists have developed metal-containing catalysts to assist in the reduction reactions that convert it to methane and other carbon-containing small molecules. Alternatively, bacteria can use CO₂ to make methane, but they use a series of proteins to catalyze the transformation.

Lance Seefeldt at Utah State University and his colleagues study a bacterial enzyme called a nitrogenase, which reduces nitrogen gas (N₂) to ammonia (NH₃) using a cluster of iron and molybdenum atoms buried inside the protein. The reduction of carbon dioxide to methane requires a transfer of eight electrons, just as ammonia production does, so the scientists wondered if an altered version of this enzyme could accept and reduce carbon dioxide.

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