Why some nitrogen-processing enzymes are more efficient than others

Only certain microbes carry the enzymes called nitrogenases, which can break apart nitrogen gas and convert it into ammonia — something most living things can't do. These enzymes come in three varieties based on their metal content, and the ones containing molybdenum are the most efficient. But why molybdenum? MIT researchers just uncovered the answer. Molybdenum doesn't bind to nitrogen directly. Instead, per MIT News, it helps nearby iron atoms bind nitrogen more strongly — and that initial binding is the critical bottleneck. Two new papers published Thursday in the journal Chem show that molybdenum's large atomic orbitals overlap with iron's, making it easier for iron to donate electrons to nitrogen. Without that electronic teamwork, iron has to do all the work alone. The discovery could guide engineers designing enzymes to reduce fertilizer needs, or synthetic catalysts that could produce ammonia using less energy than the industrial Haber-Bosch process.

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