Nitrogenase/oxidoreductase, component 1 Enzymes belonging to this family include cofactor-requiring nitrogenases and protochlorophyllide reductase. The key enzymatic reactions in nitrogen fixation are catalysed by the nitrogenase complex, which has two components, the iron protein (component 2), and a component (component 1) which is either a molybdenum-iron, vanadium-iron or iron-iron protein. The enzyme (<db_xref db="EC" dbkey="1.18.6.1"/>) forms a hexamer of two alpha, two beta and two delta chains. Protochlorophyllide reductase (<db_xref db="EC" dbkey="1.3.1.33"/>) is involved in the light-dependent accumulation of chlorophyll, probably at the step of reduction of protochlorophyllide to chlorophyllide.