Glutamine: Function & Diseases

Glutamine is a non-essential proteinogenic amino acid. It plays a central role in the organism in all metabolic processes and in building proteins. Glutamine is most abundant in the free pool of amino acids.

What is glutamine?

Glutamine represents a non-essential amino acid, which contains an acid amide group in addition to the amino group characteristic of amino acids. Nonessential means that it can be synthesized in the body. In its L-form, it is a proteinogenic amino acid. In the following, when glutamine is mentioned, it always refers to L-glutamine. In the pool of free amino acids, glutamine has the highest percentage (20 percent). One of its main functions is to act as an amino group donor. That is, glutamine is responsible for the transfer of amino groups. Furthermore, glutamine is closely related to the amino acid glutamic acid. The difference between the two compounds is that glutamine contains an acid amide group instead of the acid group of glutamic acid. Thus, a constant conversion of both amino acids into each other takes place during the transfer of amino groups. In its free form, glutamine is a colorless, crystalline solid with a melting point at 185 degrees. It is moderately soluble in water but insoluble in alcohols and some other organic compounds. Because the hydrogen ion of the acid group migrates to the amino group, glutamine exists as a zwitterion. However, it appears neutral to the outside world because the positive and negative charges are within the same molecule.

Function, action, and roles

Glutamine performs important functions in the organism. For example, it appears as a metabolite in almost all metabolic processes. It is an essential building block of almost all proteins. Its content is particularly high in muscle cells. Furthermore, its requirement is greatly increased in very metabolically active tissues. This is especially true for tissues and cells with a high rate of profiling. Since the immune system must constantly produce new cells to defend itself against germs, a particularly large amount of glutamine is needed here for protein synthesis. The demand is also extremely high in the case of trauma, injuries and severe infections. However, since the production of glutamine does not increase, its content in the free amino acid pool drops dramatically under these conditions. Another function is the aforementioned transfer of amino groups from molecule to molecule. When amino acids are broken down, glutamine transports the amino group to the liver, where it is then broken down to ammonia and excreted via the kidneys. In muscle cells, glutamine causes water to be stored in the cells during physical exertion. This is considered a signal for the build-up of proteins, so that anabolic processes are initiated. Thus, muscle building is significantly supported by glutamine. Glutamine also fulfills important functions in the nervous system. The chemically related compound glutamic acid (glutamate) functions as a neurotransmitter. After excitation conduction, glutamate is transported from the synaptic cleft into the glial cells. For reuptake into the synaptic neurons, glutamate must first be converted into glutamine. There, glutamine is converted back into glutamate. Furthermore, glutamine has been found to increase memory performance. Among other things, it also promotes the formation of the neurotransmitter GABA, which inhibits the transmission of stimuli in the nerve cells. Therefore, it also acts as a sedative and allows the body to better cope with stressful situations.

Formation, occurrence, properties, and optimal values

Glutamine is constantly synthesized in the human organism from other amino acids. Absolutely necessary for its biosynthesis are the essential amino acids leucine and valine. Both amino acids together with isoleucine represent the BCAAs as a mixture of essential amino acids, which are very important for muscle building. With a sufficient and balanced diet, the need for BCAAs and thus glutamine should be covered. In some situations, more glutamine is consumed than can currently be produced. However, a greatly reduced concentration does not increase glutamine production in the body. In that case, it should be supplied more through the diet. Particularly rich in glutamine are cottage cheese, soybeans, wheat flour and meat.

Diseases and disorders

It has been found that in severe diseases such as pancreatitis or severe infections, the concentration of free glutamine in the amino acid pool drops dramatically. The same is true in cases of trauma and injury.In these cases, the body has a higher demand for glutamine due to the large number of new cells being created. However, its biosynthesis does not increase. The high content of glutamine represents a precautionary measure of the body to survive the severe health crisis. In these situations, sufficient glutamine should be supplied via the diet. Whether an additional administration is useful has not yet been conclusively clarified. Contradictory study results are available. For example, the additional administration of glutamine in severely ill patients with multiple organ failure showed no effect or even an increased mortality rate. It is possible that the organism can also adapt to low glutamine concentrations. Perhaps even symptoms of poisoning occur in this group of patients when the dose is increased. Additional administration in healthy individuals usually has no negative consequences. Intake is recommended to increase memory performance and for increased muscle building. However, it should always be remembered that in high-risk individuals with serious diseases, intake can also be counterproductive. In connection with glutamine, however, glutamate should also be considered. Glutamate, as glutamic acid, is an amino acid related to glutamine. Increased intake of glutamate can cause tingling in the throat, flushing, nausea and even vomiting. Because Chinese food is particularly heavily flavored with glutamate, these symptoms are referred to as Chinese restaurant syndrome.