Ammonia assimilation table

In 1980, Miflin and Lea pointed out that much of the information on biochemical pathways has arisen from the use of mutants of bacteria and yeast larking key enzymes. They complained at the time that no mutants of higher plants were available in the ammonia assimilation pathway. A glance at Table I clearly indicates that a number of such mutants are now available. In addition mutants of maize with low (but not zero) levels of glutamate dehydrogenase have also been studied (Rhodes et ai, 1989). 

Extensive research and development of microbial sensors has been carried out by Suzuki et al. (89-94) and Rechnitz et al. (95-97) (see Table III). Microbial sensors consisting of membrane-bound whole cells and an oxygen electrode were constructed for the determination of substrates such as assimilable sugars, acetic acid, alcohols and ammonia, and for the estimation of biochemical oxygen demand (BOD) (98-104). Glutamic acid was determined with a microbial sensor which consists of membrane-bound whole cells containing glutamate decarboxylase and a carbon dioxide gas electrode. These microbial sensors have been applied and evaluated for on-line measurements in fermentation processes (105,106). 

Tn this volume, with several chapters devoted to the assimilation and metabolism of N-labeled ammonia and nitrate into amino acids, purines, and pyrimidines that are the building units of cellular macromolecules, it is perhaps worthwhile to consider the larger context of basic inorganic biochemistry, or how cells view and utilize the elements of the periodic table (1,2,3),... 

Inhibition patterns of [ N]ammonia accumulation by strains JL907 and JB822 (GDH") are shown in Figure 4. It is clear that assimilation plays an important role in [ N] ammonia accumulation in these strains. Strain JB822 is resistant to methionine sulfoximine due to a defect in methionine transport (data not shown). The inhibition by metabolic inhibitors (Figure 4) was not unexpected, since assimilation and all possible accumulation mechanisms (Table II) are energy-dependent. It is presently unclear whether N-ethylmaleimide inhibition was due to inactivation of a sulfhydryl-containing surface receptor or to inhibition of electron transport. 

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