Nitrogenase_MoFe_alpha_like: Nitrogenase MoFe protein, alpha subunit_like. The nitrogenase enzyme catalyzes the ATP-dependent reduction of dinitrogen to ammonia. Three genetically distinct types of nitrogenase systems are known to exist: a molybdenum-dependent nitrogenase (Mo-nitrogenase), a vanadium dependent nitrogenase (V-nitrogenase), and an iron-only nitrogenase (Fe-nitrogenase). These nitrogenase systems consist of component 1 (MoFe protein, VFe protein or, FeFe protein respectively) and, component 2 (Fe protein). This group contains the alpha subunit of component 1 of all three different forms. The most widespread and best characterized of these systems is the Mo-nitrogenase. MoFe is an alpha2beta2 tetramer, the alternative nitrogenases are alpha2beta2delta2 hexamers having alpha and beta subunits similar to the alpha and beta subunits of MoFe. The role of the delta subunit is unknown. For MoFe, each alphabeta pair of subunits contains one P-cluster (located at the alphabeta interface) and, one molecule of iron molybdenum cofactor (FeMoco) contained within the alpha subunit. The Fe protein is a homodimer which contains, a single [4Fe-4S] cluster from which electrons are transferred to the P-cluster of the MoFe and in turn, to FeMoCo the site of substrate reduction. The V-nitrogenase requires an iron-vanadium cofactor (FeVco), the iron only-nitrogenase an iron only cofactor (FeFeco). These cofactors are analogous to the FeMoco. The V-nitrogenase has P clusters identical to those of MoFe. In addition to N2, nitrogenase also catalyzes the reduction of a variety of other substrates such as acetylene The V-nitrogenase differs from the Mo- nitrogenase in that it produces free hydrazine, as a minor product during dinitrogen reduction and, ethane as a minor product during acetylene reduction.
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