Glutamate synthase, inhibition

Bacteria growing with ammonia as their sole nitrogen source use this reaction as the primary route for nitrogen assimilation, fri animal cells, the reversible reaction can function in either direction. The enzyme is allosterically regulated. ATP or GTP inhibits its action. Glutamate synthase catalyzes a similar reaction ... 

Inhibitor studies (Leaet al., 1979) have shown that the synthesis of protein from glutamine by isolated pea cotyledons is unaffected by MSO but inhibited by azaserine, consistent with the action of glutamate synthase but not very conclusive because of the side effects of azaserine. Little if any labeling data on ammonia assimilation has so far been produced using developing seeds. 

Glutamate synthases from a variety of sources exhibit classical kinetics with respect to substrates and coenzyme. High concentrations of NADPH have however been reported to inhibit the bacterial enzyme (see below). 

More recently Avila and Wallsgrove (1990) have shown that the antisera raised to barley ferredoxin-dependent glutamate synthase are able to inhibit the enzyme activity isolated from a range of plant sources. However, clear precipitation lines were detected only by Ouchterlony double-difiusion analysis with extracts from barley, wheat, rye, and rice. The enzyme from dicotyledonous and C4 plants appeared to have major differences in the amino acid composition from that purified from barley. 

---