Nitrogen stable isotope fractionation by biological nitrogen fixation reveals cellular nitrogenase is diffusion limited.

ABSTRACT: Biological fixation of dinitrogen (N₂), the primary natural source of new bioavailable nitrogen (N) on Earth, is catalyzed by the enzyme nitrogenase through a complex mechanism at its active site metal cofactor. How this reaction functions in cellular environments, including its rate-limiting step, and how enzyme structure affects functioning remain unclear. Here, we investigated cellular N₂ fixation through its N isotope effect (¹⁵ε_fix), measured as the difference between the ¹⁵N/¹⁴N ratios of diazotroph net new fixed N and N₂ substrate. The value of ¹⁵ε_fix underpins N cycle reconstructions and differs between diazotrophs using molybdenum-containing and molybdenum-free nitrogenases. By exami

SUBMITTER: Han E 

PROVIDER: S-EPMC11913218 | biostudies-literature | 2025 Mar

REPOSITORIES: biostudies-literature