Amino acids are the building blocks of polypeptides and proteins and play important roles in metabolic pathways, gene expression, and the regulation of cell signal transduction. A single organic amino acid molecule contains two functional groups, amine and carboxyl, and a unique side chain. Humans need twenty different amino acids; eleven are synthesized in the body and nine are derived from dietary sources.
Amino Acids Benefits
The benefits of amino acids are easy to name because we cannot exist without amino acids. All anatomical and physiological features of a living organism are made possible by the presence of amino acids.
The synthesis of the nutritionally non-essential amino acids alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine in the human body occurs through the de novo construction of their carbon skeletons.
However, recent studies show that we can still benefit from ingesting non-essential amino acids to promote optimal health and wellness.
Only when there are sufficient and available amounts of essential amino acids and glucose can the rate of synthesis of non-essential amino acids increase. It is therefore important to include both types of amino acids in the diet in order to benefit from their many positive, if not absolutely necessary, effects.
Essential Amino Acid Benefits
The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. These amino acids cannot be made in the body, but they are critical to an amazing array of physiological functions.
Histidine is a precursor to various hormones and metabolites important for kidney function, gastric secretion, the immune system, and neurotransmission. It helps produce red blood cells and hemoglobin.
In addition, histidine catalyzes the action of a large number of enzymes and supports anti-inflammatory and antioxidant processes. Histidine deficiency leads to anemia, renal dysfunction, oxidative stress, and inflammatory diseases.
Isoleucine is one of three branched-chain amino acids (BCAAs). It helps increase the rate of protein synthesis and promotes muscle tissue formation.
Additionally, isoleucine is known to improve glucose utilization, gut development, and immune function, although many studies have looked at BCAAs as a whole rather than as a single amino acid. This means that leucine and valine — both also essential amino acids — can share these benefits.
Lysine plays an important role in cell division and growth as it is an important building block of growth factors. Accelerated wound healing with lysine-based solutes results in less scar tissue formation, while sites that are low in oxygen and nutrients that are directly injected with growth factors benefit from angiogenesis, or the development of new blood vessels around the injection site.
In addition, lysine contributes to fat metabolism. Lysine deficiency can lead to anemia, impaired fatty acid metabolism, slow wound healing, reduced muscle mass, and the production of defective connective tissue; however, high concentrations can cause neurological disorders.
Methionine contains the element sulfur, which is essential for cartilage and liver health and improves hair texture and nail strength. Rare metabolic disorders can prevent the body from utilizing methionine, which in the long term can lead to severe liver damage from oxidative damage.
Phenylalanine is a precursor to tyrosine hydroxylase, an enzyme that accelerates catecholamine synthesis, thereby affecting mood. Phenylalanine is also required for signaling glucose availability and glucagon and insulin secretion.
It also plays a role in fat oxidation. A deficiency in phenylalanine has been linked to confusion, lack of energy, memory loss, and depression. Doses over 5,000 mg per day are toxic and can cause nerve damage.
The availability of threonine increases the absorption of other amino acids such as phenylalanine but also contributes to the balance of neurotransmitters in the brain, the production of muscle tissue, and immune system function.
Babies fed by mothers taking threonine supplements were found to have higher levels of glycine in the brain, with the subsequent risk of neurotransmitter dysfunction. As with many amino acids, the correct amounts of supplementation are not yet fixed and much more research needs to be done.
Tryptophan is a precursor molecule to niacin (vitamin B3), melatonin, and serotonin, making it essential for sleep and mood. Like all amino acids, the tryptophan codon is a building block for polypeptide chains and proteins. Tryptophan deficiency is often experienced in insomnia and depressed mood.
Non-Essential Amino Acid Benefits
The benefits of non-essential amino acids produced by the body (de novo) are likewise as broad as those of the essential group. While these amino acids are produced from scratch, dietary sources can increase availability and so provide a more reliable and consistent effect.
Alanine and glutamine molecules are synthesized in skeletal muscle using sources of pyruvate and released to increase energy supplies. Both are important for a healthy nervous system and alanine is necessary for tryptophan synthesis.
Higher levels of alanine protect the cardiovascular system, while low levels of glutamine increase mortality in critical patients and contribute to significant muscle mass loss. It is also known that glutamine is an important source of energy to tumor cells, second only to glucose.
Arginine is categorized as a conditionally essential amino acid in newborns and a non-essential amino acid in the rest of the human population. Arginine is one of the most common ingredients of polypeptides and proteins and assists to ensure a healthy immune system through increased T-cell production.
It helps to release insulin and human growth hormones, neutralize the ammonia in the liver and ameliorate skin and connective tissue quality and healing. It is also found in seminal fluid.
Asparagine plays an important role in glycoprotein synthesis and liver health. Low levels attenuate feelings of fatigue which means this amino acid is often labeled as a pick-me-up. Yet its contribution to central nervous system signaling and development is just as important as its ability to increase energy levels.
Aspartic acid works within the citric acid and urea cycles and is a precursor to other amino acids. What is more, it is also an excitatory brainstem and spinal cord neurotransmitter that increases the chance of successful postsynaptic membrane depolarization.
Its inhibitory partner is the amino acid glycine. Both of these non-essential amino acids must be in balance to be of benefit to the central nervous system. Glycine is the simplest amino acid and its calming action improves sleep and reduces reward-seeking behaviors. It can be synthesized through collagen degradation and is the primary ingredient of collagen.
Cysteine, the second and last sulfur-containing amino acid adds a thiol group (-SH) to the carboxyl and amino groups.
Cysteine is synthesized from methionine, the other sulfur-containing but essential amino acid, via transmethylation to produce homocysteine and then via transsulfuration to produce cysteine.
Cysteine is used for protein synthesis, coenzyme A synthesis, glutathione (an antioxidant), and hydrogen sulfide production. It is a precursor of pyruvate and taurine.
Glutamic acid is best known for its role as a precursor to gamma-aminobutyric acid (GABA) where an inhibitory action occurs, although glutamic acid itself acts as an excitatory neurotransmitter all over the central nervous system.
This is an extremely common dietary amino acid that may also lower blood pressure levels. Glutamate is sometimes added as a twelfth non-essential amino acid but is a derivative of glutamic acid.
Proline can be synthesized from glutamine or derived from collagen degradation and offers a source of energy when the body is under stress.
Proline production can only successfully occur in the presence of the enzyme prolyl hydroxylase and the pro factors oxygen, iron, and vitamin C. Proline is also crucial for collagen synthesis. In fact, collagen requires the presence of eighteen different amino acids in varying quantities.
Serine is necessary for the transfer of methyl groups within the body and, therefore, necessary for the production of substances such as creatine, epinephrine, DNA, and RNA. It has also been associated with breast cancer cell growth. In another form D-serine, it plays a neuromodulatory role. Furthermore, without serine, it would not be possible to form glycine, cysteine, taurine, and phospholipids.
Tyrosine has been heavily advertised as a cognitive supplement as it is a precursor of the catecholamines dopamine and noradrenaline, as well as thyroxine and melanin. However, its effects on the general population have not been proven and results tend to occur in some and not others.
Tyrosine’s action must, therefore, be dependent upon the availability or absence of other chemicals. As with every amino acid, tyrosine is also an important building block in polypeptide and protein synthesis.
The benefits of non-essential amino acids produced by the body (de novo) are just as broad as those of essential amino acids. While these amino acids are made from scratch, food sources can increase availability, allowing for a more reliable and consistent effect.
Alanine and glutamine molecules are synthesized and released in skeletal muscle using sources of pyruvate to increase energy supply. Both are important for a healthy nervous system and alanine is necessary for the synthesis of tryptophan.
Higher alanine levels protect the cardiovascular system, while low glutamine levels increase mortality in critical patients and contribute to significant muscle mass loss. It is also known that glutamine is an important energy source for tumor cells after glucose.
Arginine is classified as a conditionally essential amino acid in neonates and as a nonessential amino acid in the rest of the human population. Arginine is one of the most common components of polypeptides and proteins and contributes to a healthy immune system by increasing T-cell production.
It helps release insulin and human growth hormones neutralize the ammonia in the liver and improve skin and connective tissue quality and healing. It is also found in semen.
Asparagine plays an important role in glycoprotein synthesis and liver health. Low levels dull feelings of fatigue, meaning this amino acid is often referred to as a pick-me-up. However, its contribution to signaling and central nervous system development is just as important as its ability to increase energy levels.
Aspartic acid acts in the citric acid and urea cycles and is a precursor to other amino acids. In addition, it is also an excitatory neurotransmitter of the brainstem and spinal cord, which increases the chance of successful postsynaptic membrane depolarization.
Its inhibitory partner is the amino acid glycine. These two non-essential amino acids must be in balance to be beneficial to the central nervous system. Glycine is the simplest amino acid and its sedative effects improve sleep and reduce reward-seeking behavior. It can be synthesized through collagen breakdown and is the main component of collagen.
Cysteine, the second and last sulfur-containing amino acid, adds a thiol group (-SH) to the carboxyl and amino groups.
Cysteine is synthesized from methionine, the other sulfur-containing but essential amino acid, by transmethylation to make homocysteine, and then by transsulfurization to make cysteine.
Cysteine is used for protein synthesis, coenzyme A synthesis, glutathione (an antioxidant), and hydrogen sulfide production. It is a precursor to pyruvate and taurine.
Glutamic acid is best known for its role as a precursor to gamma-aminobutyric acid (GABA), where an inhibitory effect occurs, although glutamic acid itself acts as an excitatory neurotransmitter throughout the central nervous system.
This is an extremely common dietary amino acid that can also lower blood pressure. Glutamate is sometimes added as the twelfth non-essential amino acid but is a derivative of glutamic acid.
Proline can be synthesized from glutamine or derived from the breakdown of collagen and provides a source of energy when the body is under stress.
Proline can only be successfully produced in the presence of the enzyme prolyl hydroxylase and the profactors oxygen, iron, and vitamin C. Proline is also crucial for collagen synthesis. In fact, collagen requires the presence of eighteen different amino acids in varying amounts.
Serine is necessary for the transfer of methyl groups in the body and thus necessary for the production of substances such as creatine, epinephrine, DNA, and RNA. It has also been linked to the growth of breast cancer cells. In another form, D-serine plays a neuromodulatory role. In addition, without serine, it would not be possible to form glycine, cysteine, taurine, and phospholipids.
Tyrosine has been heavily promoted as a cognitive supplement because it is a precursor to the catecholamines dopamine and norepinephrine, as well as thyroxine and melanin. However, the effects on the general population have not been proven and the results tend to occur in some and not in others.
The effect of tyrosine must therefore depend on the availability or absence of other chemicals. Like any amino acid, tyrosine is an important building block in polypeptide and protein synthesis.
Amino Acid Structure
The amino acid structure is among the easiest structures to recognize, as every organic molecule has an alkaline (or basic) amino functional group (-NH2), an acidic carboxyl functional group (-COOH), and a unique organic side chain (R chain) associated with each amino acid. In fact, the name of this group is a summary of the core ingredients – alpha-amino [α-amino] and carboxylic acid.
All amino acids contain a single, central carbon atom. The amino and carboxyl functional groups are attached to this central carbon atom, often referred to as the α-carbon. This leaves two of the four carbon bonds free.
One binds to one of the abundant hydrogen atoms nearby, the other binds to an organic side chain or R group. R groups possess a variety of shapes, sizes, charges, and reactions that allow amino acids to be grouped according to the chemical properties generated by their side chains.
Aliphatic Amino Acids
Aliphatic amino acids are non-polar and hydrophobic. Hydrophobicity increases with an increasing number of carbon atoms in the side chain. The aliphatic amino acids are alanine, glycine, isoleucine, leucine, proline, and valine; Despite having so few carbon atoms, glycine is neither hydrophilic nor hydrophobic.
Methionine is sometimes referred to as an honorary member of the aliphatic group. Its side chain contains a sulfur atom instead of carbon and hydrogen atoms, but like the aliphatic group, it does not react strongly in the presence of other molecules because aliphatic amino acids do not have a positive or negative charge, instead, they have an even distribution of charge across the molecule.
Aromatic Amino Acids
The aromatic amino acids include phenylalanine, tyrosine, and tryptophan, and have little to no charge. These molecules vary between hydrophobic (phenylalanine and tryptophan) and non-hydrophobic (tyrosine).
The word aromatic refers to the attachment of a highly stable aromatic ring that does not readily react with other compounds or elements. Aromatic compounds, also known as aryl compounds, are abundant in the human body. Every nucleotide in our DNA and RNA is made up of aromatic molecules.
Histidine is sometimes incorrectly listed within the aromatic group. Its amino groups can be aromatic but are reactive with a weak positive charge and hydrophilic properties.
Basic Amino Acids
While their name indicates that all amino acids have acidic properties, some have basic (alkaline) side chains that contain nitrogen. These basic R chains bind to available protons (hydrogen molecules) giving them a positive charge. The amino acids in this group are all hydrophilic.
The three basic amino acids are arginine, lysine, and histidine. Arginine has the strongest positive charge of any amino acid due to three nitrogen groups, which is essential to its ability to synthesize proteins and catalyze enzyme function. Lysine also has a strong positive charge, while histidine has a very weak positive charge due to its lack of nitrogen in the amino group.
Acidic Amino Acids
Acidic amino acids consist of aspartic acid and glutamic acid. Of course, these are easy to identify because of the word “acid” in the compound’s name, although these two amino acids are sometimes referred to as aspartate and glutamate, which can be confusing.
Instead of nitrogen groups, acidic amino acids have carboxylic acid groups as side chains. As acids, they can give off protons when reacting with other compounds or elements and are therefore negatively charged. Acidic amino acids are hydrophilic
Hydroxylic Amino Acids
Another small group with only two amino acids is the hydroxylic amino acids serine and threonine. These uncharged polar and hydrophilic molecules have a hydroxyl group as the R chain.
Sulphur-Containing Amino Acids
Only cysteine and methionine contain sulfur atoms and are therefore the only members of this group. Cysteine can combine with cysteine through a disulfide bond to form an oxidized dimer called cysteine, which is found in large amounts in connective tissue, hair, fingernails, and toenails.
In the case of sulfur-containing amino acids, the side chain consists of a thiol group (-SH). If you notice the letter S in an amino acid’s chemical structure, you can be sure it’s either cysteine or methionine.
Cysteine is the smaller of the two molecules and is essentially an alanine molecule with an extra thiol group. Methionine contains a thiol ether with two pendant groups on either side of the sulfur atom, making it extremely hydrophobic.
Amidic Amino Acids
The side chain of the amidic amino acids has an amide group (-CONH2) and should not be confused with the amine side group of the amino acids lysine, arginine, and histidine.
The amide formed from glutamic acid is called glutamine and the amide formed from aspartic acid is called asparagine. It is therefore easy to understand why amidic amino acids can only do their work in the presence of sufficient glutamic acid and aspartic acid.
Asparagine is a very hydrophilic, uncharged amide of aspartic acid that does not react with other molecules. Similarly, glutamine has no charge and is hydrophilic, and is an amide of glutamic acid.
Protein and Amino Acids
Protein and amino acids are essentially a dependency relationship. Amino acids are monomers, molecules that bind to other molecules to form polymers. In the case of amino acids, they bind to produce oligopeptides of no more than twenty amino acids or longer polypeptide chains, which can then fold to form proteins. Amino acid sequences are based on an original section of the genetic code extracted from DNA.
Protein synthesis occurs within the cell, where portions of the genetic code are copied into the nucleus and transported to the cell’s cytoplasm via messenger RNA. Messenger RNA (mRNA) is copied after being fixed between the large and small parts of a ribosome. This is possible through the action of transfer RNA.
Transfer RNA (tRNA) is attached to an amino acid. A strand of mRNA has ten to a hundred codons, each of which is a group of three nucleotides that code for a single amino acid. When the transfer RNA recognizes a codon, it deposits its attached amino acid inside the ribosome, where it binds to the previous amino acid to form a chain.
In the table above, each of the non-essential amino acids is encoded by a series of codons. For example, the code that tells the tRNA to bring serine has six different forms – UCU, UCC, UCA, UCG, AGU, and AGC.
Different tRNAs deliver their supplies of amino acids in order and according to each codon present on the strand of messenger RNA. The result is a growing oligopeptide or polypeptide chain assembled according to a specific amino acid sequence that conforms to the instructions of the code copied from nuclear DNA. Once the chain is complete, it is released from the ribosome and matures into a functional peptide or protein according to its length and shape.
Protein structures can be primary, secondary, tertiary, or quaternary depending on the degree of folding that occurs. The primary structure consists only of peptide bonds made between the two parts of the ribosome.
Secondary structure refers to hydrogen bonds that create sections of spirals that compress the original chain structure. The tertiary structure adds salt bridges, more hydrogen bonds, and disulfide bonds to create an even more compact package.
Finally, the quaternary structure involves two or more polypeptide chains that function as a single entity or multimer. These four structures are simply shown in the image below.
Amino Acids Function
Amino acids work in a variety of ways. Recent years have shown that amino acids are not only building blocks and cell signaling molecules but also regulators of gene expression and protein phosphorylation cascades.
We also know that they are precursors to hormones and nitrogenous substances and have unprecedented biological importance. In addition, some amino acids regulate important metabolic pathways required for maintenance, growth, reproduction, and immunity.
Despite this, increased levels of amino acids and the results of their synthesis in the form of ammonia and homocysteine can cause neurological disorders, oxidative stress, and cardiovascular diseases.
We are still in the infancy of amino acid research and their full range of functions is still largely unknown, as is the ability of amino acids to function as a group or within an overall system. Optimal amino acid balance in the diet is critical but is largely poorly understood, making it impossible to publish solid guidelines.
Dietary supplements containing the functional amino acids arginine, cysteine, glutamine, leucine, proline, and tryptophan have been shown to be beneficial for a range of health-related disorders at every stage of life, from fetal to geriatric populations, intestinal dysfunction, obesity, diabetes, and cardiovascular diseases, metabolic disorders, and infertility.
In addition, amino acids are consumed by sports enthusiasts and athletes to increase muscle mass and reduce fat gain; however, cognitive side effects and kidney damage associated with amino acid supplementation have been reported.
Amino Acids Examples
See this article for examples of amino acids. It might be more interesting to look at one of the best current amino acid supplements on the market and discuss its positive and negative effects.
One of the most popular amino acid supplements is a blend of branched-chain amino acids (BCAAs), namely leucine, isoleucine, and valine. BCAAs are said to stimulate muscle protein synthesis by more than 30%. That’s just not possible.
The first reason is that some degree of muscle breakdown has to take place in order to release essential amino acids; The rate of production of new muscle tissue depends on the rate of breakdown of old muscle cells.
Second, higher dietary sources of a limited group of amino acids will not reach high levels if other amino acid levels remain normal or low. With research still having a long way to go, any nutritional advice regarding the intake of amino acids should be taken at face value.
Branched-chain amino acids are indeed linked to the synthesis of muscle tissue, but each amino acid, essential and non-essential, is linked in some way to the same function. Although muscle protein is in a constant state of turnover, the levels and ratios of available amino acids may not always be optimal.
In addition, all amino acids compete for the same carrier molecules. BCAAs use the same carrier system that transports the aromatic amino acids phenylalanine, tyrosine, and tryptophan.
The subsequent performance is therefore also limited to the possibility of transport; Saturation of supplements can prevent other important amino acids, which are present in normal amounts, from reaching their target. High levels of BCAAs compete with carrier molecules for aromatic amino acids, which are important for neurotransmitter synthesis. The result can affect mood.
BCAAs are believed to play an important role in intracellular signaling pathways involved in protein synthesis. This has proven itself many times but focuses on a small window. BCAA supplements are known to relieve symptoms associated with liver cirrhosis and chronic kidney failure. Other claims have not yet been adequately substantiated.
It’s also worth remembering that diabetics and the overweight naturally have high levels of BCAAs and low levels of alanine. Athletes may be interested to hear that elevated blood levels of ammonia are present after BCAA administration during exercise, suggesting that supplementation may ultimately have a negative impact on muscle performance.
Another worrying effect has been noted in cancer patients, where BCAAs promote cancer growth and are used by tumors as an energy source.