Glutamine, biosynthesis hydrolysis

Nevertheless the biosynthesis of glutamine proceeds from glutamic acid The dif ference is that the endergonic process m Equation 1 is coupled with the strongly exer gome hydrolysis of ATP... 

Condensation of CO2, ammonia, and ATP to form carbamoyl phosphate is catalyzed by mitochondrial carbamoyl phosphate synthase I (reaction 1, Figure 29-9). A cytosolic form of this enzyme, carbamoyl phosphate synthase II, uses glutamine rather than ammonia as the nitrogen donor and functions in pyrimidine biosynthesis (see Chapter 34). Carbamoyl phosphate synthase I, the rate-hmiting enzyme of the urea cycle, is active only in the presence of its allosteric activator JV-acetylglutamate, which enhances the affinity of the synthase for ATP. Formation of carbamoyl phosphate requires 2 mol of ATP, one of which serves as a phosphate donor. Conversion of the second ATP to AMP and pyrophosphate, coupled to the hydrolysis of pyrophosphate to orthophosphate, provides the driving... 

Histidine can be prepared from imidazole as in Scheme 117. It is a basic amino acid, the biosynthesis of which appears to involve adenosine 5 -phosphate, ribose phosphate and glutamine (which supplies a nitrogen for the imidazole ring) (Scheme 118). Histidine is one of the most important amino acids and has involvement in such biological processes as ester hydrolysis, acylation and (by virtue of its complexing power with iron) oxygen... 

As stated above, the only other known route for the biosynthesis of PLP is dependent upon R5P, G3P, and glutamine, and is catalyzed by a single enzyme complex. The PLP synthase holoenzyme complex consists of 12 synthase (Pdxl) subunits and 12 glutaminase (Pdx2) subunits that form into a cogwheel-type structure (Figure yj 36.39,41,42,59 subunits decorate the exterior of this cogwheel and catalyze the hydrolysis of... 

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