This deep-sea enzyme survives heat that destroys most proteins

A deep-sea microbe uses an exceptionally heat-resistant enzyme to turn atmospheric nitrogen into ammonia at temperatures that would destroy most proteins. Its unusual structure and a newly observed reaction state may reveal an ancient, shared mechanism behind nitrogen fixation and could eventually inspire cleaner biotechnology and fertilizer production. This deep-sea enzyme survives heat that destroys most proteins.

One example is nitrogen fixation, a process that converts nitrogen gas (N 2) into a form living organisms can actually use. Nitrogen makes up about 78 percent of Earth’s atmosphere, but plants and animals cannot use it directly because the two nitrogen atoms in N 2 are joined by an exceptionally strong chemical triple bond. Certain microorganisms have evolved a way around this problem.

They can break that bond and transform N 2 into ammonia, which can then be incorporated into biological molecules. One of these organisms is the deep-sea archaeon Methanocaldococcus infernus, which lives in volcanic marine environments where vent fluids can reach temperatures above the boiling point of water. Researchers in Tristan Wagner’s laboratory at the Max Planck Institute for Marine Microbiology in Bremen wanted to understand how this organism performs nitrogen fixation under such extreme conditions.