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Nitrogenase is an enzyme responsible for catalyzing nitrogen fixation, which is the reduction of nitrogen (N 2) to ammonia (NH 3) and a process vital to sustaining life on Earth. [9] There are three types of nitrogenase found in various nitrogen-fixing bacteria: molybdenum (Mo) nitrogenase, vanadium (V) nitrogenase, and iron-only (Fe ...
The nif genes are genes encoding enzymes involved in the fixation of atmospheric nitrogen into a form of nitrogen available to living organisms. The primary enzyme encoded by the nif genes is the nitrogenase complex which is in charge of converting atmospheric nitrogen (N 2) to other nitrogen forms such as ammonia which the organism can use for various purposes.
Nitrogenase is thought to have evolved sometime between 1.5-2.2 billion years ago (Ga), [38] [39] although some isotopic support showing nitrogenase evolution as early as around 3.2 Ga. [40] Nitrogenase appears to have evolved from maturase-like proteins, although the function of the preceding protein is currently unknown. [41]
FeMoco (FeMo cofactor) is the primary cofactor of nitrogenase. Nitrogenase is the enzyme that catalyzes the conversion of atmospheric nitrogen molecules N 2 into ammonia (NH 3) through the process known as nitrogen fixation. Because it contains iron and molybdenum, the cofactor is called FeMoco. Its stoichiometry is Fe 7 MoS 9 C.
Structure of the FeMoco cluster in nitrogenase. The cluster is linked to the protein by the amino acid residues cysteine and histidine. Nitrogenase include two P-clusters ([8Fe-7S]) and two FeMocos ([7Fe-9S-C-Mo-R homocitrate]). [8] Carbon monoxide dehydrogenase and acetyl coenzyme-A synthase each features an Fe-N-iS 4 clusters. [9] [10]
Nitrogenase is the most important enzyme involved in nitrogen fixation. Azotobacter species have several types of nitrogenase. The basic one is molybdenum-iron nitrogenase. [43] An alternative type contains vanadium; it is independent of molybdenum ions [44] [45] [46] and is more active than
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Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc, Cylindrospermum, and Anabaena. [1] They fix nitrogen from dinitrogen (N 2) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis. [2]