Glutamate-ammonia ligase

Glutamate-ammonia ligase (EC 6.3.1.2) couples the following two reactions ... 

The glutamate-ammonia ligase reaction is glutamate + ATP + ammonia = glutamine + ADP + Pi... 

FIGURE 16.2 Incorporation of ammonia into biomolecules, (a) Glutamate dehydrogenase reaction, (b) Glutamate-ammonia ligase reaction... 

Glutamine synthetase (GS L-glutamate ammonia ligase, ADP forming EC 6.3.1.2) is quite different from the enzymes considered previously in that it is always present in mammals. The basic reaction is common to all life forms (Figure 2.7). Glutamine is synthesized for incorporation into proteins but also serves as an amino or amido donor for a host of biosynthetic reactions (Figure 2.8). 

GMP synthetase [EC 6.3.4.1], also known as xanthosine-5 -phosphate ammonia ligase, catalyzes the reaction of ATP with xanthosine 5 -phosphate and ammonia to produce GMP, AMP, and pyrophosphate (or, diphosphate). GMP synthetase (glutamine-utilizing) [EC 6.3.5.2] catalyzes the reaction of ATP with xanthosine 5 -phosphate, L-glutamine, and water to produce GMP, AMP, L-glutamate, and pyrophosphate. 

This enzyme [EC 6.S.4.2], also referred to as UTPiam-monia ligase, catalyzes the reaction of UTP with ATP and ammonia (or glutamine) to produce CTP, ATP, and orthophosphate (and glutamate if glutamine had been used as the nitrogen source). 

Ligase reactions necessarily involve coupling. As a first example, consider reaction 6.3.1.2 glutamate + atp + ammonia = glutamine + adp + pi (All-1)... 

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