Glutamine: Biosynthesis of glutamine from glutamate is catalyzed by glutamine synthesis, and enzyme present in high quantities in renal tissue. This reaction is similar and different to that of glutamate dehydrogenase. Both fix inorganic nitrogen-but one into amino and other into amide linkage. Both are exergonic reactions-glutamine synthetase the hydrolysis of ATP (Adenosine triphosphate), and glutamate dehydrogenase the oxidation of NAD (P) H (Nicotanamide adenine dinucleotide phosphate).
As the ammonia is constantly produced in the tissues, so is removed from the circulation by the liver and converted to glutamate, glutamine, and finally to urea. Only traces of ammonia (10-20 mcg/dl) are present in peripheral blood.
Glutamine aynthetase fixes ammonia as glutamine. Since certain tumors exhibit very high requirements for glutamine and asparagines, the asparaginase and glutaminase have been used as antitumor agents. Catabolism of glutamine and of glutamate is similar to that of asparagines and aspartate but forms fo ketoglutarate. The deamidation of glutamine is catalysed by glutaminase. Antifolate drugs or glutamine analogs block purine nucleotide biosynthesis.
Glutamic acid is a dicarboxylic amino acid and is readily synthesized in the body. It is known as aminoglutaric acid, and most reactive amino acid metabolically. It is synthesized in the body through the process of
* transamination,
* dehydrogenation,
* by glutaminase, a hydrolyzing enzyme.
It is catabolised to form a ) detoglutaric acid, and b) glutamine through glutamine synthetase, and enzyme. The glumatic acid content in the brain is high. Glutathione is tripeptide and contains glutamic acid, cystine and glycine. The glutamic acid helps in synthesis of praline, aspartic acid, and ornithine. Glutamine along with glucose works as fuel for brain cells, and also as detoxifier of ammonia from the brain. In systematic acidosis, glutamine is released from muscle, glutamine uptake by the liver is decreased and glutamine release is increased. More glutamine is therefore present in the circulation, and renal production of ammonia increases.
Glutamine is formed in the liver, kidney, brain, and retina. Glutamine serves as a reservoir of nitrogen in tissues. Glutamine takes part in the process of detoxication in which phenylacetic acid, the toxic substance of the body is excreted with the formation of phenyl acetyl glutamine. Glutamine participates in synthesis of purine, histidine, NAD and NADP, and pyrimidine.
Folic acid, or folate, consists of the base pterdine attached to one molecule each of PABA (p-aminobenzoic acid) and glutamic acid. The yeast, liver, and leafy vegetables are major sources of folates.
