Amino Acids Biological Importance and Origins
One of the two molecule groups that built the first single-celled organisms on earth. Formed 3.8 billion years ago. The perfect setup; DNA and RNA with the ability to self-replicate and continue progressing life, DNA storing and recording every step of this process, and RNA transcribing sections of the DNA called genes and translating the information to build proteins. Evolution, is caused by genetic variance, when information stored in the DNA is altered, subsequently creating new modified protein structures, either for the better, worse, or neutral effect to the organism. Survival fuels evolution, DNA records and stores changes caused by evolution, RNA copies the new information, and protein carries out the modified functions.
Amino acids all have the same basic structure; an alpha carbon tetrahedral atom, a carboxyl group, a hydrogen atom, and the differentiator - a unique R-chain group. The R side chain is different for each individual amino acid.
Generally people think of amino acids as molecules derived from protein. People also may or may not run into amino acid supplements along the way, without further inquiry, a few supplements, comments, and a basic understanding of biology they come away with minimum appreciation. While amino acids are really one of the first two molecular groups that composed cellular life, build every protein inside your body (which are involved in nearly every process), and are vital to metabolic balance and maintaining a healthy life.
Amino Acids In Humans
Humans require 22 proteinogenic amino acids, 13 can be produced endogenously (ranging from: non-essential, to semi and conditionally essential), the remaining 9 are classified essential amino acids (the body can not produce them internally, and therefore must derive them from food). Amino acids importance starts at the very beginning of life; DNA, the nucleic acid that stores and records biological information, is really just storing and recording protein structure blueprints. Genes, the sections of DNA containing protein structures, are a sequence of nucleotides that, RNA, the messenger nucleic acid copies (with one nucleotide nuance) and then decodes in the ribosomes of a cell. The nucleotide sequence is decoded in pieces called codons, i.e., three nucleotides in a row - each codon pertaining to a individual amino acid. https://viviolifesciences.com/pages/protein-synthesis
Genes can be turned on or off, controlled by transcription factors (proteins, i.e., built from amino acids). Humans have approximately 22,000 genes, which in terms of different species on earth is relatively low, for example a water flea has around 31,000 genes. Biological complexity is based on the network of genes, and the interaction of genes throughout history as to advance species and evolve new protein structures.
Amino Acids Build Biochemical Proteins
Enzymes, cell adhesion compounds, hemoproteins, storage and transport molecules, hormones and growth factors, DNA-binders and RNA-binders, receptor molecules, immune system molecules, signaling and regulatory proteins, sensory, and many more aspects of a living organism are governed, determined, and/or built from or by proteins. Proteins are the most versatile macromolecules in the human body, there would be no advanced life forms without them, and every single protein out there is built from a selection of just 22 proteinogenic amino acids.
Protein synthesis is an intracellular process, fundamental to cellular life, and integral to living organism’s survival.
L-Form v.s. D-Form
Except for glycine, every proteinogenic amino acid naturally occurs in two isomeric forms (isoleucine, and threonine can occur in four), D-form and L-form. Difference being the direction of rotation of the chemical structure, amino acids being chiral compounds, since they contain an asymmetric center carbon. Have molecular mirror images that can not be stacked, and are non-superimposable.
How does this impact you? Simply; only L-form amino acids are active and used in cells. D-form amino acids are sometimes found in cells walls, but for general health purposes are not important.
Ketogenic v.s. Glucogenic (or both)
Amino acids are a backup fuel in living organisms, the liver will start to convert amino acids and fatty acids when cellular glucose is low/depleted. Amino acids either produce ketone bodies (ketogenic), or amino acids produce glucose (glucogenic), fourteen exclusively glucogenic amino acids, three exclusively ketogenic, and five that are both (produce either ketone bodies or glucose).
Ketogenic amino acids are; leucine, lysine, and pyrrolysine.
Glucogenic amino acids are; alanine, cysteine, glycine, serine, asparagine, aspartic acid, methionine, valine, arginine, glutamic acid, glutamine, histidine, proline, and selenocysteine.
Both; amino acids that can produce either ketone bodies or glucose are; isoleucine, tryptophan, phenylalanine, tyrosine, and threonine.
All 22 Proteinogenic Amino Acids: Classification, Name, Description, Codon(s), and Food Sources
Essential Amino Acids:
1. L-Histidine: This alpha amino acid exhibits anti-inflammatory, and antioxidant qualities in humans. An important molecule in fighting reactive oxygen species (ROS). Histidine is also medically used in large quantities for rheumatoid arthritis therapy, allergic reactions, kidney disorders, and ulcers. Histidine is precursor to histanime, an important immune response organic nitrogenous compound. Histidine is one of the two amino acids that compose carnosine, a dipeptide that exerts powerful anti-aging properties. Histidine is encoded by codons, CAU, and CAC. Food sources include; buckwheat, eggs, cauliflower, mushrooms, potatoes, bamboo shoots, bananas, cantaloupe, lamb, tuna, chicken, and kamut wheat. https://pubchem.ncbi.nlm.nih.gov/compound/L-histidine
2. L-Isoleucine: One of the three branched chain amino acids (BCAA), associated with insulin resistance, regulating blood sugar and energy levels. BCAAs are widely used in the weightlifting and fitness community as energy, muscle growth, recovery, and protein building amino acids. Isoleucine is an effective nitrogen donor and transporter. Isoleucine has two chiral centers, meaning it can occur in four stereoisomers. Isoleucine is encoded by codons, AUU, AUA, and AUC. Food sources include; eggs, salmon, milk, pork, chicken, wheat germ, legumes, beef, lima beans, and oats. https://academic.oup.com/jn/article/136/1/324S/4664150 https://pubchem.ncbi.nlm.nih.gov/compound/l-isoleucine#section=Top
3. L-Leucine: One of the three branched chain amino acids (BCAA), the most abundant of the three. Regular diet provides sufficient supply of Leucine an amino acid important in metabolic regulation. One of the BCAAs, it is often studied for its proposed muscle growth, repair, and recovery attributes. Leucine can be found in bodily tissue and biofluids. Studies regarding the use of BCAAs in high intensity exercise training have mixed conclusions, some report increases in lean muscle mass protection and increased fat loss, while other findings lack of significance. Leucine is encoded by codons, CUU, CUC, CUA, CUG, UUA, and UUG. Food sources include; chicken, cheddar cheese, legumes, tuna, pumpkin seeds, octopus, peanuts, and white beans. https://pubchem.ncbi.nlm.nih.gov/compound/L-leucine#section=Top
4. L-Lysine: This essential amino acid is involved in tissue repair, and growth. Chemically, L-Lysine competes with L-Arginine for cellular absorption, sharing common metabolic pathways, the two amino acids are at odds, high supply of one often denotes a lessor or silenced supply of the other. Low lysine levels have frequently appeared in a number of psychological conditions, such as; depression, and stress-induced physical disorders. Lysine is the single precursor to the new amino acid (22nd), pyrrolysine. Lysine is encoded by codons, AAG, and AAA. Food sources include; fermented soybeans, seitan protein, lentils, black beans, quinoa, soy milk, pistachios, pumpkin seeds, and turkey. https://pubchem.ncbi.nlm.nih.gov/compound/L-lysine#section=Top
5. L-Methionine: Is one of only two sulfur containing amino acids. Sulfur an essential macronutrient in living organisms, with an atomic mass of 16. The essential amino acid methionine, serves as a very important sulfur containing dietary component. Sulfur strengthens and supports, skin, hair, nails, protects cells, aids the absorption of other macronutrients, and slows adverse aging. Methionine itself is a heavy metal chelator. Methionine is also a precursor to other amino acids, along with antioxidants. Couple the impact of methionine as a metal chelating agent, and precursor to multiple antioxidants, methionine makes the case of being a detoxification molecule in living organisms. Methionine is encoded by the codon, AUG. Food sources include; brazil nuts, beef, parmesan cheese, chicken, pork, snapper fish, yogurt, and soybeans. https://pubchem.ncbi.nlm.nih.gov/compound/L-methionine#section=Top
6. L-Phenylalanine: An aromatic amino acid, necessary precursor to dopamine, melanin, noradrenaline, and thyroxine. Phenylalanine is also a precursor to other amino acid structures, and is highly concentrated in the brain and plasma. Phenylalanine is an amino acid that can cross the blood-brain barrier. Phenylalanine is also used in artificial sweeteners. There is a genetic condition called phenylketonuria (PKU), which causes phenylalanine to build up in the body, PKU is a defect in the particular gene that produces the enzyme required to break down phenylalanine. PKU is a rare inherited genetic disorder, and the people living with PKU must follow a strict diet that limits phenylalanine intake, reducing protein consumption, and no artificial sweeteners. Phenylalanine is encoded by codons, UUC, and UUU. Food Sources include; pearled barley, mung beans, kidney beans, chickpeas, goat cheese, soy flour, and pork shoulder. https://pubchem.ncbi.nlm.nih.gov/compound/L-phenylalanine
7. L-Threonine: Is a polar/hydrophilic amino acid found in many important protein structures; amelogenin proteins that develop and compose tooth enamel, elastin, and collagen. Supporting the nervous system, immune system, and fat metabolism. L-Threonine is used in Lou Gehrig’s disease therapy, yet more studies are required to determine the impact of Threonine as a therapy. Threonine has two chiral centers, consequently threonine can occur in four stereoisomers. Threonine is also a precursor to the amino acid glycine. L-Threonine is encoded by codons, ACA, ACC, ACG, and ACU. Food sources include; turkey, veal liver, chicken liver, romano cheese, trout and snapper fish, whelks, cuttlefish, lobster, watermelon seeds, and yellow beans. https://pubchem.ncbi.nlm.nih.gov/compound/L-threonine#section=Top
8. L-Tryptophan: Precursor to both, serotonin, and melatonin. Considered the least abundant amino acid in living organisms, yet thoroughly important. Serotonin is a neurotransmitter that regulates mood, sleep, and appetite, often referred to as the “happy chemical.” Melatonin is a hormone produced in the pineal gland, the production of which is linked to the time of day (increases when dark, decrease when light out), melatonin is a sleep hormone. L-Tryptophan is often supplemented, and advertised for people who have depression, anxiety, or trouble sleeping. Niacin (vitamin B3) is synthesized from L-Tryptophan in the liver, a very important nutritional conversion. Tryptophan is encoded by codon, UGG. Food sources include; eggs, chocolate, chia seeds, tofu, wild boar, halibut, clams, wheat germ, and lentils. https://pubchem.ncbi.nlm.nih.gov/compound/L-tryptophan#section=Top
9. L-Valine: One of the three branched chain amino acids (BCAA). A hydrophobic amino acid, known for tissue repair and muscle growth, along with the other two BCAAs. L-Valine acts as a nitrogen transporter, and donator. Valine is apart of the synthesis of the neurotransmitter, glutamate. L-Valine is also a precursor to antibiotics. Valine helps support the three-dimensional structure of globular proteins. Athletes mind their L-Valine intake, through diet and supplementation, due to L-Valines positive lean body muscle mass protection qualities. Valine is a glucogenic amino acid (can be converted to glucose in the liver), which is activated to protect skeletal muscle. Valine is encoded by codons, GUG, GUC, GUA, and GUU. Food sources include; cottage cheese, whole milk, bacon, navy beans, white mushrooms, seaweed, elk, and eggs. https://pubchem.ncbi.nlm.nih.gov/compound/L-valine#section=Top https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:16414 https://viviolifesciences.com/pages/l-valine
Nonessential & Conditionally essential
10. L-Alanine: A nonessential amino acids, the human body can produce alanine internally. Alanine is synthesized from pyruvic acid, pyruvic acid is made from glucose during glycolysis, alanine can also be synthesized from the branched chain amino acids. L-Alanine is the second most prevalent amino acid in protein structures. The alanine-glucose cycle in the liver is an important glucose conversion for regulating blood sugar. The beta form of alanine is the other amino acid, along with histidine that together build carnosine, a dipeptide that fights oxidative stress. Alanine is encoded by codons, GCG, GCC, GCU, and GCA. Food sources include; gelatin, seaweed, eggs, corn, soybeans, and watercress. https://pubchem.ncbi.nlm.nih.gov/compound/L-alanine#section=Top
11. L-Arginine: A conditionally essential amino acid (when the body is experiencing stress, endogenous production may not be enough, or may be inhibited, meaning the body must source more from diet), widely recognized as the most versatile proteinogenic amino acid. L-Arginine is the sole precursor to the natural vasodilator nitric oxide, a gas that relaxes blood vessels. L-Arginine is also a precursor to enzymes Agmatine, and Creatine. L-Arginine is also present in urea molecules. Supporting skin, hair, and nails, through healthy elastin, keratin, and collagen protein production. L-Arginine and its production of nitric oxide, increase blood flow, and help a myriad of health issues/areas. Studies have shown oral L-Arginine supplementation to reduce systolic, and diastolic blood pressure, and a host of other abilities in double blind placebo trials. Arginine is encoded by codons, AGA, AGG, CGG, CGC, CGA, and CGU. Food sources include; spirulina, turkey, soybeans, lentils, pumpkin seeds, sunflower seeds, peanuts, and walnuts. https://viviolifesciences.com/pages/l-arginine https://pubchem.ncbi.nlm.nih.gov/compound/L-arginine
12. L-Asparagine: A nonessential amino acid, the human body can produce asparagine endogenously. Asparagine was first isolated by french chemists, Louis Nicolas Vauquelin, and Pierre Jean Robiquet, from asparagus juice. Asparagine was the first amino acid to be discovered, and they named it after the food they isolated it from. Asparagine serves as a bonding site for carbohydrates to attach to proteins, a carbohydrate covalently bonds with the amide nitrogen atom in the R-group, i.e., side chain of asparagine, to create N-linked glycoproteins. Glycoproteins are units of cell membranes, functions include; cell adhesion (i.e. sperm to egg adhesion), cellular structure, hormone molecules, and cell-to-cell interaction. Asparagine is also a natural diuretic, helping the body produce more urine and subsequently removal of excess fluids and waste. Asparagine is encoded by codons, AAC, and AAU. Food sources include; asparagus, potatoes, legumes, whole grains, eggs, and whey protein. https://www.ncbi.nlm.nih.gov/books/NBK22521/ https://pubchem.ncbi.nlm.nih.gov/compound/L-asparagine#section=Top
13. L-Aspartic acid: A nonessential amino acid, the human body can produce aspartic acid internally. At a neutral pH, aspartic acid is one of only two amino acids that have an acidic R-group (side chain). Aspartic acid combines with minerals to aid absorption. Aspartic acid ionic form known as, aspartate, plays a role in the citric acid cycle (krebs cycle), the third process in cellular respiration. The krebs cycle is an energy capturing process that starts with acetyl CoA, and produces multiple different molecules. Aspartate is also involved in the urea cycle. Aspartic acid is encoded by codons, GAC, and GAU. Food sources include; cabbage, halibut, egg whites, soy protein, tofu, gelatin, bacon, spirulina, cod, beef, bison, and peanuts. https://pubchem.ncbi.nlm.nih.gov/compound/L-aspartic_acid#section=Top
14. L-Cysteine: A conditionally essential amino acid (when the body is experiencing stress, endogenous production may not be enough, or may be inhibited, meaning the body must source more from diet). Cysteine is one of only two sulfur containing amino acids. L-Cysteine is a precursor to glutathione, a powerful tripeptide antioxidant, it fights reactive oxygen species to protect cells from oxidation aging/damage. Cysteine is an important metal-binding agent and regulator, cysteine also regulates redox activities. Cysteine residue is also found in mycothiol molecules, a detoxification agent. Cysteine is involved in the production of; taurine amino acid, a multitude of proteins, and biotin. L-Cysteine is encoded by codons, UGC, and UGU. Food sources include; soy flour, lamb, beef, watermelon seeds, pistachios, chia seeds, chicken, wheat germ, mussels, eggs, yellow beans, swiss cheese, shrimp, turkey, and quinoa. https://www.sciencedirect.com/science/article/pii/S1074552103001741 https://viviolifesciences.com/pages/l-cysteine
15. L-Glutamic acid: A nonessential amino acid, the body can produce glutamic acid endogenously. Glutamic acid becomes glutamate. Glutamate serves as the primary excitatory neurotransmitter in the central nervous system, playing an important role in learning and memory. Glutamate works by sending chemical messages from nerve cell to nerve cell, proper function require a balance of glutamate. Glutamic acid is a precursor to amino acid, glutamine, arginine, and proline. Folic acid (a B vitamin) derivatives, folates or folacin, incorporate at least one molecule of glutamic acid. Sodium glutamate, the salt form of glutamic acid is used in the food industry as monosodium glutamate, otherwise known as MSG - a salt flavor enhancer. Glutamic acid is encoded by codons, GAG, and GAA. Food sources include; tomatoes, walnuts, peas, chicken, eggs, parmesan cheese, tofu, cod, almonds, romano and provolone cheese, veal, and seaweed. https://pubchem.ncbi.nlm.nih.gov/compound/L-glutamic_acid#section=Top
16. L-Glutamine: A conditionally essential amino acid (when the body is experiencing stress, endogenous production may not be enough, or may be inhibited, meaning the body must source more from diet). Through research glutamine classification was changed to conditionally essential, due to the massive use of glutamine by immune, gastrointestinal, and renal cells during; illness, trauma, infection, bowel conditions, and physiological stress. Glutamine is the most copious free form amino acid in humans, important for gastrointestinal health. Glutamine regulates tight junction proteins, barrier, partition, cellular protection, and leakage preventing macromolecules. Glutamine also assists enterocyte cells (intestinal absorptive cells), supporting intestinal lining cells. Glutamine is a precursor to Glutathione an important antioxidant. Glutamine has anti-inflammatory effects in the gastrointestinal system, glutamine interacts with prostaglandins (lipid compounds), prostaglandins are lipids that act like hormones, inflammation mediating molecules, serving as vasodilators, signalor for white blood cells, and regulator of clotting. Glutamine regulates cellular integrity, gastrointestinal cell apoptosis, and general gut health. Glutamine is being clinically tested for its potential efficacy as an irritable bowel syndrome (IBS), and Crohn's disease therapy. Glutamine is encoded by codons, CAG, and CAA. Food sources include; red cabbage, eggs, yogurt, mozzarella cheese, spinach, pistachios, kale, almonds, carrots, walnuts, beets, beef, chicken, papaya, brussel sprouts, and celery. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5622680/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5454963/ https://gut.bmj.com/content/early/2018/08/14/gutjnl-2017-315136.long
17. L-Tyrosine: A conditionally essential amino acid (when the body is experiencing stress, endogenous production may not be enough, or may be inhibited, meaning the body must source more from diet). Tyrosine oxidation, then polymerization produces melanin, i.e., pigmentation molecules. Tyrosine is also active in the thyroid gland, where it is bonded with iodine to create thyroid hormones. Neutral L-Tyrosine can cross the blood-brain barrier, where it serves as a precursor for catecholamines; dopamine, epinephrine, and noradrenaline. L-Tyrosine has shown a maintenance quality in cognitive function during physiological stress. Tyrosine is encoded by codons, UAU, and UAC. Food sources include; blue cheese, tofu, steak, pork ribs, tuna, crab, shrimp, chicken, turkey, sesame seeds, yogurt, sour cream, split peas, and raw oats. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1863555/
18. L-Glycine: A conditionally essential amino acid (when the body is experiencing stress, endogenous production may not be enough, or may be inhibited, meaning the body must source more from diet). Glycine is an inhibitory neurotransmitter in the central nervous system, the main inhibitory neurotransmitter in the spinal cord. Glycine inhibitory neurotransmitter processes sensory and motor movement information. Glycine is one of the amino acids involved with, one carbon pool, utilized to biosynthesize choline, creatine, purine, and also perform methylation of nucleic acids. Glycine is encoded by codons, GGG, GGA, GGU, and GGC. Food sources include; gelatin, pickled pork, chicken, pastrami, lamb, corned beef, pork skins, turkey, seaweed, veal, bison, soy protein isolate, amaranth grain, quail, and duck. https://pubchem.ncbi.nlm.nih.gov/compound/glycine#section=Top
19. L-Proline: A conditionally essential amino acid (when the body is experiencing stress, endogenous production may not be enough, or may be inhibited, meaning the body must source more from diet). Structurally proline is different then the basic amino acid molecule, the side chain comes from the central atom per usual, but then it forms a ring and connects to the nitrogen of the amino group. Due to this ring proline does not have a primary amino group, the ring atoms act as a secondary amino group and R group (side chain) at the same time. Due to this structural abnormality, when proline is incorporated in protein structures it is a rigid unit that often causes kinks in the folding shape of the protein. Proline is biosynthesized from glutamic acid. L-Proline composes a decent amount of the polypeptide chain for the protein, collagen. Proline is encoded by codons, CCG, CCC, CCA, and CCU. Food sources include; gelatin, cottage cheese, cabbage, parmesan, pork skins, chives, watercress, cucumber, alfalfa sprouts, asparagus, buckwheat, soy protein isolate, beef, colby cheese, and yogurt.
20. L-Serine: A conditionally essential amino acid (when the body is experiencing stress, endogenous production may not be enough, or may be inhibited, meaning the body must source more from diet). L-Serine is required for p-selectin proteins cytoplasmic domain, serine also serves as the phosphorylation site for p-selectin proteins. In response to UV radiation cell damage, the protein p53 can regulate cellular apoptosis, and growth, p53 protein relies on serine as its phosphorylation site; p53 protein is a transcription factor protein that responds to damaged DNA signals. Transcription factors can turn genes on or off through the epigenetic system, therefore p53 has the ability to suppress/silence damaged DNA/oncogenes to prevent UV-irradiated/damaged genes from proliferating or creating compromised proteins. Serine being the phosphorylation site of p53 protein serves as an expression regulator of the transcription factor protein, expression required after suffering genetic damage, p53 is also known as the tumor suppressor protein. Serine also has a positive impact on the expression of glutathione peroxidase (GPx), an important enzyme antioxidant compound. L-Serine is also required for phosphatidylserine synthesis, a phospholipid that protects neurons in the brain - prompting clinical studies of l-serine supplementation as a potential treatment or prevention mechanism of neurodegenerative diseases. Serine is encoded by codons, UCC, UCU, UCG, UCA, AGC, and AGU. Food sources include; eggs, spirulina, turkey, elk, cottage cheese, buffalo, cod, milk, pumpkin seeds, parsley, salmon, kidney beans, pistachios, wheat germ, and peanuts. https://viviolifesciences.com/pages/l-serine http://www.jbc.org/content/275/27/20444.long https://www.ncbi.nlm.nih.gov/pmc/articles/PMC321447/
21. L-Selenocysteine: A nonessential amino acid, the body produces selenocysteine internally, however selenocysteine is best classified as a non-standard amino acid. The 21st amino acid, discovered in 1986, by Thressa Stadtman. A non-standard amino acid due to its incorporation as a stop codon, UGA. This particular amino acids is a cysteine structure with a selenium chain rather than a sulfur containing chain, hence the name. Selenium is a mineral involved in antioxidant enzyme production. Selenocysteine is both encoded and is incorporated in proteins by and as the codon, UGA. Food sources are cysteine food sources, and selenium food sources, which are; brazil nuts, cottage cheese, brown rice, cashews, spinach, oysters, and shiitake mushrooms. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3065758/
22. L-Pyrrolysine: A nonessential amino acid, the body produces pyrrolysine endogenously, however pyrrolysine is best classified as a non-standard amino acid. The 22nd amino acid, discovered in 2002. A non-standard amino acid due to its incorporation as a stop codon, UAG. Food sources for pyrrolysine are food sources of the essential amino acid lysine and an alkaline supply for chemical compounds that are apart of the pyrrolysine structure.
*This is not to be taken as medical advice, or to diagnose, treat, or cure any illness. These statements have not be viewed or approved by the FDA.