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Unlocking the Power of Amino Acids

Amino acids are units that are combined to form proteins. There are 20 different amino acids, and all of these are used by your body to function properly. The amino acids are further divided into essential and non-essential amino acids. Nine of these amino acids are listed under the essential category, meaning we need to acquire these amino acids through our diet. Food that contains these amino acids mostly includes red meat, dairy, and eggs. The remaining amino acids are classified as non-essential, these amino acids can be synthesized by the body as required.

Proteins are large complex molecules that have a specific sequence of amino acids combined (Campbell et al., 2016). Their specific sequence aids the proteins in folding into different shapes in order to perform their functions throughout the body. Your body contains thousands of proteins, each of which plays a vital role in maintaining your health.

In a way, amino acids are like Lego blocks: by combining different blocks in different ways, you create different objects. Similarly, amino acids can be combined in different ways to make different proteins. Another characteristic of an amino acid is that it is an organic compound, which contains carbon, nitrogen, oxygen, and hydrogen atoms that are together. All amino acids have the same basic structure. It has a central carbon atom with four different groups attached to the carbon atom, an amino group, a carboxyl acid group, a hydrogen and an R-group (better described as a side chain). The figure below shows alanine, the amino acid with a methyl side chain as the R-group (Figure 1).

Figure 1: The general structure of an amino acid – alanine

We identify amino acids by their R-groups, which are also responsible for their functional and chemical roles. The various amino acids are shown in Figure 2 below. When amino acids are bonded together, they form a simple molecule with a single loss of water to form an amide or better known as a peptide bond. This bond occurs directly between the amino group of one amino acid and the carboxyl group of another amino acid. Once they are bonded together, the structure is identified as a protein and the formation of the amino acids allows the protein to fold into a three-dimensional structure (Tyers & Mann, 2003). As mentioned before, proteins are made in vivo by the combination and reaction between different amino acids. Therefore, amino acids are involved in many important roles in the body, for instance, the breakdown of food, body tissue repair, neurotransmitters and hormone synthesis, a source of energy, muscle building, boosting the immune system and maintaining a healthy digestive system.

Figure 2: 20 Different amino acid structures

Complete proteins are foods that contain all nine essential amino acids. These include red meats, white meats, dairy, eggs, quinoa, buckwheat and soy. Some foods do not contain all nine essential amino acids and are referred to as incomplete proteins i.e. nuts, seeds, beans and some grains. In order to consume all nine essential amino acids on a vegetarian or vegan diet, you should consume several types of incomplete proteins.

Calming and Energizing Amino Acids

A neurotransmitter is a chemical messenger that carries messages from nerve cells to target cells. Essentially, they facilitate communication between neurons. Neurons release chemical signals in vesicles, or sacs, through the synapse, which are then converted to neurotransmitters and transported to the receiving neuron. In order to understand the message being sent, the receiver must respond in a specific way. It is estimated that there are over 100 different types of neurotransmitters in the body. There are two types of neurotransmitters; (i) small molecules, such as amino acid derivatives, and (ii) neuropeptides (Cooper, 2001).

A variety of hormones are produced by two amino acids, tyrosine and tryptophan. The products are known as monoamine derivatives (norepinephrine, epinephrine, serotonin, and dopamine), which are usually degraded or deactivated by the enzyme monoamine oxidase (MAO).

Serotonin (5-Hydroxytryptophan) is a chemical that is constructed from tryptophan (Figure 3). Serotonin and dopamine are both involved in moods, depression, digestion, and sleep. Epinephrine and norepinephrine, more widely known as adrenaline and noradrenaline, are also produced from the building blocks; tyrosine and phenylalanine (Figure 3). During this conversion, dopamine is formed as an intermediate. They are all classed as catecholamines. Located above your kidneys are two small glands called adrenal glands, which produce catecholamines. L-Dihydroxyphenylalanine (L-DOPA) is another intermediate in the biosynthetic conversion of tyrosine, having low levels of L-DOPA is associated with Parkinson's disease. Tyrosine and phenylalanine supplements might increase the levels of dopamine, though L-DOPA, the immediate precursor, is usually prescribed due to the fact that L-DOPA is taken up much more quickly in the body (Byrne et al., 2014)

Figure 3: Biosynthetic pathways of both catecholamines and serotonin

The hormone epinephrine is commonly known as the hormone of flight or fight. As a result, glucose is released into the bloodstream, and brain functions are stimulated. People taking monoamine oxidase inhibitors stay in a relatively high mental state, sometimes too high, because the epinephrine is not degraded or broken down rapidly. Serotonin has a sedative effect, giving a pleasant feeling. Depression is associated with low levels of serotonin, while manic states are associated with extremely high levels. By controlling serotonin levels and their metabolites, manic depressive illness (also called bipolar disorder) can be managed (Byrne et al., 2014; Nutt, 2008).

For some time now, it has been reported that the amino acids tyrosine and phenylalanine may cause unexpected side effects in some people. For example, many people are reporting headaches triggered by the phenylalanine present in aspartame (a low-calorie sweetener). In addition to taking tyrosine supplements in the morning for a morning boost, some people claim that tryptophan supplements help them sleep well at night. It is widely believed that a glass of warm milk before bed helps induce sleep because milk proteins contain high levels of tryptophan. In contrast, cheese and red wine contain high levels of tyramine, which mimics epinephrine. For many people, a cheese omelet is the perfect way to start the day (Campbell et al., 2016).

Unlocking the Puzzle of Phenylketonuria

Inborn errors of metabolism are genetic diseases where the root cause can be attributed to a variety of things. The disease may be inherited or it may occur as the result of spontaneous mutations. One of these includes mutations that lead to deficiencies in enzymes, they usually involve defects in the DNA of the affected individual.

Most severe forms of mental retardation result from errors in enzymes that are needed to catalyze amino acid reactions. Phenylketonuria (PKU) is a well-known example. PKU is an inherited disorder in which the blood contains high levels of phenylalanine, phenylpyruvate and phenylacetate (Figure 4). Additionally, accumulation of these products in the brain cells may result in an osmotic imbalance that allows water to flow into the brain cells (van Spronsen et al., 2021). In the developing brain, these cells expand until they crush each other. In either case, the brain is not able to develop normally. In many countries, it is mandatory to test newborns for PKU because it is easier to treat the disease with a modified diet than it is to institutionalize an individual indefinitely. The dietary changes are relatively simple. Phenylalanine must be limited to the amount necessary for protein synthesis, and tyrosine must be supplemented (van Spronsen et al., 2021). Foods containing aspartame may carry warnings about its phenylalanine content. A substitute for aspartame sweeteners contains alanine and is sold under the trade name alatame.


Figure 4: Healthy person versus an individual with PKU (Phe - Phenylalanine, Tyr – Tyrosine)

Aside from their vital roles in numerous biological processes, amino acids play an important role in health and wellness. Various body systems are supported by these building blocks of proteins, which contribute to enzyme synthesis, hormone production, neurotransmitter production, and antibody synthesis. It is also possible to get energy by digesting amino acids when carbohydrates and fats are not available. Amino acids are not only important in protein synthesis, they as well contribute in cellular signaling pathways, gene expression, and nutrient transport. Glutamine supports the immune system, while tryptophan is a precursor to serotonin, an important molecule that affects mood and sleep.

In summary, amino acids maintain proper bodily functions and human health. It is crucial to understand their significance and ensure that an appropriate intake is maintained in order to promote overall well-being and optimize various physiological processes.

Bibliographic references

Byrne, J. H., Heidelberger, R., & Waxham, M. N. (2014). From molecules to networks: an introduction to cellular and molecular neuroscience. Academic Press.

Campbell, M. K., Farrell, S. O., & McDougal, O. M. (2016). Biochemistry. Cengage Learning.

Cooper, J. R. (2001). Neurotransmitters. In N. J. Smelser & P. B. Baltes (Eds.), International Encyclopedia of the Social & Behavioral Sciences (pp. 10612-10619). Pergamon. DOI:

Nutt, D. J. (2008). Relationship of neurotransmitters to the symptoms of major depressive disorder. J Clin psychiatry, 69(Suppl E1), 4-7.

Tyers, M., & Mann, M. (2003, 2003/03/01). From genomics to proteomics. Nature, 422(6928), 193-197. DOI:

van Spronsen, F. J., Blau, N., Harding, C., Burlina, A., Longo, N., & Bosch, A. M. (2021). Phenylketonuria. Nature reviews Disease primers, 7(1), 36.

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Nicole Galetti

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