Glutamine

General Features:

Glutamine facts

Abbreviated: Gln or Q

Molecular formula: C₅H₁₀N₂O₃

Molar mass: 146.14 g mol⁻¹

pKA:  2.17 (-COOH), 9.13 (α-NH₂)

Physiological Roles:

• Glutamine is an amino donor for many compounds; the ones to note are the pyrimidines and the purines. It is a non-toxic transporter of ammonia in the blood.
• It may also donate its carbon atoms to the citric acid cycle in order to replenish the cycle. 
• Glutamine is involved in a cycle with glutamate. Glutamate becomes Glutamine when it picks up an amino group with the help of an ATP. The ability to synthesize Glutamine and Glutamate is detrimental to a cell because it the only route to incorporate inorganic nitrogen into cell material. To learn more go to your library and read pages 244-246 in  The Physiology and Biochemistry of Prokaryotes,Third Edition by David White.

Synthesis:

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Going from glutamate to glutamine involves the removal of the OH group (pictured at the top of the molecule) and replacing it with PO3- donated from ATP. ATP is what drives the reaction to completion. The intermediate is then replaced with a amino group thus producing Glutamine. This is all done with the help of L-glutamine synthase enzyme.

Glutamate/Glutamine cycle (Plant Biochem)

Pictured above is the glutamate/glutamine synthesis cycle. Under conditions of low ammonia concentration bacteria use two enzymes, L-glutamine synthase (GS) and glutamate synthase. L-glutamine synthase is the enzyme which incorporates the ammonia into the glutamate to form glutamine. The glutamate synthase enzyme transfers the incorporated ammonia from glutamine to α-ketoglutarate to form glutamate. (Learn more from pages 244-246 in  The Physiology and Biochemistry of Prokaryotes,Third Edition by David White.)