Nitrogen assimilation is a fundamental biological process that occurs in plants and algae that are incapable of independent nitrogen fixation. The assimilation of nitrogen has marked effects on plant productivity, biomass, and crop yield, and nitrogen deficiency leads to a decrease in structural components. Initial conversion of nitrate to nitrite (by nitrate reductase) is followed by a reduction to ammonia by nitrite reductase (also called nitrite oxidoreductase). The ammonia is incorporated into glutamine as an amido nitrogen and is reductively transferred to 2-oxoglutarate to form 2 molecules of glutamate by glutamate synthase. The general steps of assimilation have been known for several years, however, the chemical mechanisms that occur in these processes remain poorly understood in large part due to the lack of detailed structural information concerning the enzymes that catalyze these reactions.