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Amino acids are, on the one hand, the smallest building blocks of a protein, but on the other hand, they also fulfill independent functional roles. Those amino acids that are used to build proteins are called "proteinogenic".
Furthermore, a distinction is made between essential and non-essential amino acids:
- Essential amino acids: Must be obtained through food; a deficiency cannot be compensated for by the body itself.
- Non-essential amino acids: Can be produced in the body using essential amino acids.
Over 400 amino acids are known so far, of which 20 are "proteinogenic" in humans – d.h...serve to build proteins. And 9 of the &400 amino acids are “essential”, d.hThey must be obtained through food and cannot be produced by the body itself.
Amino acids are fatty acid derivatives (carboxylic acid derivatives) with an amino group at the α-C atom ("α-amino carboxylic acids")
Classification of amino acids
- According to chemical structure
- branched-chain or unbranched-chain
- sulfur-containing or non-sulfur-containing
- aromatic (with a benzene ring of 6 carbon atoms in the side chain) or aliphatic (non-aromatic)
- According to essentiality
- Essential/Semi-essential amino acids (must be supplied)
- Non-essential AS (can z.B. are formed in the citric acid cycle by transamination from 2-oxocarboxylic acids)
- After tasks
- Functional tasks:
- Structural functions (anabolic function): Building of oligopeptides and proteins (currently 23 amino acids recognized, z.B. ornithine, citrulline, taurine)
- Energy production (catabolic function)
- Provision of sulfur
- Medical tasks:
- Prevention, z.BHormone replacement therapy (L-arginine)
- Therapy, z.BImmunology, oxidative stress, cardiology, psyche
- Functional tasks:
The most important amino acids
a) Essential
- Isoleucine (VK, k, g, *)
- Leucine (VK, k, *)
- Lysine (k, *)
- Methionine (SH, g, *)
- Phenylalanine (AS, k, g, *)
- Threonine (g, *)
- Tryptophan (AS, k, g, *)
- Valine (VK, g, *)
- Histidine (AS, g, *
- Arginine (g *)
- Cystine/Cysteine (SH, g, *)
- Tyrosine (AS, k, g, *)
- Alanine (g, *)
- Aspartic acid/
- Asparagine (g, *)
- Glutamic acid (g, *)
- Glutamine (g, *)
- Glycine (Glycocol, g, *)
- Serine (g, *)
Proline (g, *)
Ornithine - Taurine (SH)
- Hydroxyproline
- Citrulline
- 3-Methylhistidine
- GABA
- Theanine
* = amino acids used for protein synthesis
k = ketogenic
g = glycogen
SH = Sulfur-containing AS
VK = Branched-chain AS
AS = Aromatic AS
Catabolic vs. anabolic pathway
Digestible proteins ingested through food are broken down into their components (amino acids) and added to the amino acid pool. The utilization of these amino acids then occurs either "catabolically" or "anabolically."The catabolic pathway describes the use of amino acids for energy production in the mitochondria; the anabolic pathway describes the use of amino acids for the building of proteins.
Functions of proteins (made up of amino acids) in humans
| protein | function | Examples |
| Structural proteins | Support structure of the organism | Collagen, hair, nails, matrix, elastin, keratin, myosin |
| Contractile proteins | Components of the musculature | Myosin, actin |
| Enzymes | Catalysis of many biochemical reactions, antioxidant and anti-inflammatory function | Amylase, lipase, pepsin, trypsin, catalases, peroxidases, proteases |
| Transport and carrier proteins | Transport of important molecules | Hemoglobin, plasma albumins, calcium-binding protein, metallothioneins |
| Regulatory proteins | Control and coordination of chemical reactions | Hormones (z.B.insulin, oxytocin, insulin, glucagon, corticotropin, vasopressin, angiotensin) |
| Protective proteins | Storage of substances for future needs | Blood clotting (thrombin, fibrin, fibrinogen), immune system (immunoglobulins, interleukins), storage proteins (ferritin = iron storage) |
| Control proteins | Regulation of various processes in the organism | Correctly reading the DNA |
Amino acids as precursors of the body's own substances
| Precursors of other amino acid derivatives (oligopeptides) |
|
| Lysine + Methionine | Carnitine |
| Phenylalanine + Tyrosine | Coenzyme Q10 |
| Glutamate + Glycine + Cysteine | Glutathion |
| Arginine + Glycine (+ Cofactor Methionine) | Creatine (Methylguanidine Acetic Acid) |
| Cysteine (+ Vit. B5 + ADP) | Coenzyme A |
| Glutamate + Glycine + Cysteine (+ Vit B3 + Chromium) | Glucose tolerance factor |
| Arginine, Ornithine (+ SAM) | Polyamines (spermidine, putrescine, spermine) |
| Arginine | Nitric oxide (NO) |
| Precursors of neurotransmitters (biogenic amines) |
|
| Phenylalanine -> Tyrosine | Adrenaline, noraderenalin, thyroxine, tyramine (sympathomimetic) |
| Tryptophan | Serotonin, melatonin |
| Histidine | histamine |
| Glutamic acid (glutamate) | Gamma-Aminobutyric Acid (GABA), Glutamine |
An overview of the most important amino acids
L-Lysine
- Essential amino acid
- Basic amino acid
- Carnitine building block (cofactors Fe, Vit. C, B3)
- Effects:
- Cardiovascular protective function: building block of vascular collagen, atherogenic potential of Lp(a) â, possible release of deposited Lp(a)'s
- Important for the immune system (v.a. in viral infections (reduces virus replication)
- Increases intestinal Ca++ absorption (possibly(useful in osteoporosis)
L-Methionine
- Essential amino acid
- Neutral sulfur-containing amino acid (main source of sulfur)
- S-Adenosylmethionine (SAM) = biologically active form
- Precursor of homocysteine and thus of cysteine, cystine, taurine (B vitamins and methionine are essential for homocysteine metabolism and the 1-carbon pathway!)
- Carnitine building block
- Effects:
- Most important methyl group donor and therefore highly relevant in the context of epigenetics and longevity research ("healthy longevity")
- binds heavy metals for detoxification (z.B(Copper, cadmium and mercury)
- acidifies the urine
- It has an antioxidant effect (supports the effect of selenium)
- important for the immune system
L-tryptophan
- essential amino acid
- Aromatic amino acid
- Precursor of serotonin (and melatonin)
- Precursor of kynurenine formation
- Effects:
- Sleep-promoting
- immune system
- Antibody response via kynurenines
- Monocytes and IL1 production
- Production of vitamin B3 (niacin) or NAD via kynurenine (primarily in the liver)
- Protein and acetyl-CoA formation
- Blood pressure lowering (especially in combination with vitamin B6): probably through serotonergic effects
- Deficiency risk z.B. in case of fructose intolerance and lactose intolerance (reduced absorption in the intestine), because undigested lactose binds tryptophan and prevents its absorption.
(Source: www.fxmayr.com/de/medicine-nutrition-lactose.aspx; https://vgxii.com/attack-of-the-tryptophan/)
Tryptophan-serotonin-melatonin synthesis
L-Arginine
- Semi-essential amino acid
- Basic amino acid formed from citrulline and aspartate or from ornithine
- Effects:
- Precursor of nitric oxide (NO)
- Signaling substance
- antioxidant, cytotoxic, antimicrobial, stimulates neutrophils
- Vasodilating, reduces platelet aggregation and blood pressure, improves blood flow (similar to prostaglandin E1)
- Stimulates anabolic somatotropin (STH = "Hormone of Fasting"); STH increases protein synthesis and mobilizes fat deposits
- Stimulates anabolic insulin-like growth factor 1 (IGF-1)
- Important for the (cellular) immune system
- Important for collagen synthesis
- Improves perfusion after ischemia
- Precursor of nitric oxide (NO)
- Practical tip:
- Fractionated administration in several small doses between meals
- Herpes proteins rich in arginine (possiblyActivation of latent infections):
Therefore, arginine should not be used as monotherapy for herpes simplex infections:
Combination with lysine (acute 3x1 g/day, preventive 500 mg/day) in a ratio of 1:2
L-Carnitine
- Amino acid derivative
- Formed from methionine and lysine
- Effects:
- Energy metabolism (L-carnitine as a “biocarrier”): Transport molecule for free long-chain fatty acids in mitochondria for beta-oxidation (95% of occurrence in cardiac and skeletal muscle)
- Performance-enhancing (z.B(Sports, Cardiology)
- Influence on blood lipid levels
- membrane-stabilizing, antioxidant and neuroprotective
- Important for the immune system
- Detoxification function: Liver metabolism of toxic substances; transport molecule ("biocarrier") of toxic metabolites for excretion via the kidneys
Coenzyme Q10
- Amino acid derivative
- Formed from geranylgeranyl phosphate (via the mevalonic pathway or acetyl-CoA via all-trans-decaprenyl phosphate) and from tyrosine (via hydroxybenzoic acid)
- Effects:
- Energy metabolism: Central component of the respiratory chain (inner mitochondrial membrane)
- Antioxidant in lipophilic phase (concerning arteriosclerosis, cancer, accelerated aging, etc.))
- Localization in mitochondria: particularly good and rapid local effect on oxygen radicals.
- Involved in the reduction of oxidized vitamin E
- Caution: Statin administration reduces coenzyme Q10 production (from mevalonic acid)
Examples of amino acid (and derivative) indications
A) Immune system
- Amino acids are building blocks of immune cells.
- Amino acids are building blocks of:
- Immunoglobulins
- Interferons (antiviral and antiproliferative glycoproteins of leukocytes)
- Interleukins (stimulate the growth and differentiation of lymphocytes)
- Lysozyme (dissolves bacterial walls)
- Thymus factors (stimulate maturation of T lymphocytes and proliferation of lymphatic tissue)
- Amino acids (and derivatives) have an antioxidant effect
- Amino acids stabilize the non-specific mucosal block
- Amino acids affect T-cell regulation
- Amino acids stimulate the specific humoral immune response
- Tryptophan is a kynurenine precursor
| substance | Examples of effects |
| Arginine | T-cell stimulation, phagocytosis modulation (neutrophils, monocytes), antimicrobial, |
| Lysine | Regulation of NO |
| Methionine | Methyl group donor in the immune system |
| Taurine | anti-inflammatory |
| Threonine | Stimulation of lymphocyte proliferation, synthesis of mucus protein in the intestinal immune system, |
| Tryptophan | Inhibition of pro-inflammatory cytokines, production of kynurenines, increase in immunity |
| Carnitine | T cell stimulation, phagocytosis modulation (neutrophils, monocytes) |
| Glutathion | Regulation of cell metabolism (z.B. Leukotriene production, apoptosis), immune response |
| Creatine | Antiviral activity |
(Source: Arndt) &Albers, Handbook of Protein and Amino Acids, p. 55, Li P et al.; Amino acids and immune function. Br J Nutr 2007;98(2):237-52)
B) Diabetes
- Increased use of amino acids for gluconeogenesis (amino acids as energy carriers)
- Increased formation of fatty acids and ketone bodies from amino acids (due to high amounts of acetyl-CoA and overload of the citric acid cycle)
- Amino acid derivatives have an antioxidant effect (in cases of high oxidative stress)
- Amino acids can stimulate insulin release (insulin improves amino acid uptake into cells)
- Insulin (a peptide hormone) contains disulfide bridges and requires sulfur.
- Important amino acids for diabetes:
- L-Carnitine (reduces acetyl-CoA and lowers ketone bodies)
- L-Arginine, Phenylalanine, BCAAs (insulin release)
- L-Cysteine (u.a.Component of GTF, essential for CoA formation, S-supplier)
- Aspartic acid (lowers ketone bodies)
- Glutathione, taurine (antioxidant, sulfur supplier)
C) Cardiovascular system
- Amino acids are relevant to the cardiovascular system.
- Vasodilation (widening of blood vessels)
- Vascular protection
- Energy supply
- Radical degradation and reduction of lipid peroxidation
- Important amino acids for the cardiovascular system:
- L-Arginine (NO and vasodilation)
- L-Cysteine (improves NO function)
- Taurine (positive inotropic, antiarrhythmic, antioxidant)
- L-Lysine (stabilizes vessel walls, reduces the atherogenic potential of Lp(a))
- L-tryptophan and tyrosine (BP-lowering neurotransmitters)
- L-Carnitine and Coenzyme Q10 (Energy)
- Glutathione (antioxidant)
D) Liver
- Amino acids prevent destruction of the (liver) cell membrane
- Formation of structural proteins (z.B. Liver cell membrane)
- Formation of liver-specific enzymes and functional proteins
- Amino acids maintain complex detoxification functions: the liver must detoxify ammonia (formed during protein catabolism) in the urea cycle.
- Important amino acids for the liver:
- L-arginine, ornithine, aspartic acid, citrulline
- L-cysteine (sulfate, glutathione)
- Branched-chain amino acids (in cirrhosis)
E) Gastrointestinal tract
- Proteins are broken down in the gastrointestinal tract:
- Protein digestion begins in the stomach
- Pepsin as a key enzyme (acid-controlled)
- Peptones as breakdown products (stimulate duodenal cholecystokinin and exocrine pancreas)
- Absorption disorders (z.B(e.g., due to illness) lead to amino acid deficiency.
- The gut, in turn, requires amino acids. for its function (z.BCell membrane structure, energy for intestinal flora, detoxification, bile acid metabolism)
- Important amino acids (and derivatives) with intestinal mucosa-protective and digestion-promoting effects: Methionine, glutamine, histidine, threonine, tryptophan and glutathione
Key amino acids (and derivatives) in the gastrointestinal tract
| substance | functions && Effects |
| Methionine | Cofactor in the formation of melatonin and CoA (involved in the formation of cell membrane phospholipids of the intestinal mucosa) Important for Formation of active short-chain fatty acids (formed by physiological intestinal flora with mucosa-protective and anti-cancer properties) Important for the barrier function and integrity of the colonic mucosa |
| Glutamine | Main energy source of the mucosal cells and precursor for the Nucleotide biosynthesis of rapidly dividing intestinal mucosal cells. Improves intestinal mucosa. Metabolic stress (surgeries, burns, trauma) often leads to glutamine deficiency, which results in mucosal atrophy with reduced barrier function and facilitated bacterial translocation. |
| Histidine | It affects gastric acidity and is a precursor for histamine formation (a biogenic amine with many biological effects). It increases hydrochloric acid secretion. |
| Threonine | Promotes mucosal integrity and barrier function |
| Tryptophan | Precursors of serotonin and indole (derivatives), which support barrier function, mucosal homeostasis, and the nervous system |
| Glutathion | Essential for maintaining normal intestinal mucosa. Antioxidant. |
F) Psyche
- Precursors and activators of neurotransmitters (L-Tryptophan, L-Phenylalanine, L-Tyrosine, L-Histidine)
- Effect as a neurotransmitter (z.B.glutamine, glutamate, GABA, glycine)
- Involved in the metabolism of melatonin (SAM, L-Tryptophan)
- Incorporated as protein precursors in Stress processing, hypothalamic-pituitary-adrenal axis and sleep
| Neurotransmitters | precursor | Function/Control |
| L-Glycine | L-Serine | inhibitory effect on brain activity |
| L-glutamic acid | L-Glutamine | Excitatory NTM (brain alertness); |
| L-Glutamine | L-glutamic acid | Can be converted into glutamic acid; |
| GABA | L-glutamic acid | Inhibitory NTM |
| Adrenaline/Noradrenaline | L-Phenylalanine/L-Tyrosine | More of an excitatory NTM |
| Serotonin | L-tryptophan | Rather inhibitory NTM |
| histamine | L-Histidine | It has a regulatory effect on noradrenergic, serotonergic, and cholinergic systems. |
G) Weight reduction
- Weight loss means: reducing calorie intake; consequences:
- Lower protein intake
- Gluconeogenesis and fatty acid production from amino acids á
- Breakdown of structural proteins (muscles, enzymes, immunoglobulins, transport albumin) → reduced performance, fatigue, exhaustion, premature "diet failure"
- Colloid osmotic pressure decreases with edema formation and reduced diuresis (amino acids regulate water balance)
- Important amino acids in a diet:
- Neurotransmitters and precursors (z.B. tryptophan, phenylalanine, glutamine, taurine)
- Arginine (activation of the somatotrophic hormone STH → reduces fat mass)
- Carnitine (fat burning)
H) Sport/Performance
- Structural development (especially muscle)
- Optimization of metabolism (z.BImmune system, redox system, psyche)
- Energy generation (including reserve energy)
- Antioxidant effect (high levels of free radicals during extreme sports)
- Important amino acids for performance enhancement:
- L-Carnitine (energy)
- Coenzyme Q10 (energy)
- Creatine (energy)
- Glutathione (antioxidant)
- Essential AS in particular.branched-chain amino acids as well as arginine, glutamine (structural composition)
I) Healthy longevity
- A good supply of amino acids represents a useful building block in an overall concept of "good aging".
- Amino acids are u.a. Building blocks of proteins and other essential substances
- Optimization of metabolism (z.B(Immune system, redox system, psyche, hormones)
- Optimization of the supporting tissue
- Optimization of organ functions (z.B(Cardiovascular system, nerves, skin)
- Important amino acids for “aging skin” (z.B.Dryness, wrinkles, collagen deficiency, healing)
- Arginine
- Cysteine
- Proline
- Glycine
- Mix of essential amino acids
- Spermidine
Symptoms of amino acid and protein deficiency
- Swollen eyes and legs (water shifted from blood vessels into tissue)
- Muscles become weaker (muscle loss)
- Hair becomes thinner (due to lack of keratin)
- Nails become brittle
- Skin becomes dry and flaky (wrinkles form)
- Mental alertness declines
- Fatigue and sleep disorders
- Immunodeficiency (susceptibility to infection)
- Wound healing disorders
- Micronutrient deficiency (protein transports micronutrients)
- Blood sugar fluctuations and cravings for sweets (feeling of insatiability)
Which amino acids should be tested for deficiency in the presence of specific symptoms?
| indication | Lead AS (mainly affected) |
| detoxification | Cysteine, glutamic acid, glycine |
| hair loss | Cysteine, Methionine, Tyrosine, Glutathione |
| Skin diseases | Arginine, cysteine, glutamine, lysine |
| Heart disease | Arginine, Lysine, Methionine, Taurine, Carnitine |
| Obesity | Arginine, Methionine, Phenylalanine, Tryptophan, Tyrosine |
| Gastrointestinal | Glutamine, Threonine, Methionine, Tryptophan, Glutathione |
| immune system | Lysine, methionine, arginine, tryptophan, glutamine |
| Parkinson's disease | Phenylalanine, Tyrosine, Carnitine |
Source: Ganzimmun
Examples of amino acids in food
| Methionine | Egg, whey, whole grain bread, corn, rice |
| Lysine | Meat, egg, whey, soy, potato, wheat germ, lentils |
| Leucin | Pumpkin seeds, oats, almonds, lentils, crispbread |
| Isoleucine | Meat, cheese, pumpkin seeds, oats, almonds, lentils, soy |
| Threonine | Meat, cheese, pumpkin seeds, oats, almonds, lentils, soy |
| Valin | Meat, cheese, pumpkin seeds, oats, almonds, lentils, soy |
| Phenylalanine | Meat, cheese, pumpkin seeds, oats, almonds, lentils, soy |
| Tryptophan | Cocoa powder, buckwheat, flaxseed, sesame seeds, apricot kernels, pumpkin seeds, |
| Histidine | Meat, liver, trout, tuna, cheese, lentils, sunflower seeds, lupins, soybeans |
| Arginine | Meat, fish, nuts, soy, wheat germ, brown rice, oats |
| Taurine | meat, fish |
| Glutamine | Meat, fish, soy, beans |
| Glycine | Beef, liver, peanuts, oats |
| Carnitine | Red meat, crab |
| Alanine | Beef, pork, egg whites, whey, whole corn, rice, soy, oats |
| Tyrosine | Cocoa powder, buckwheat, flax seeds, sesame seeds, apricot kernels, pumpkin seeds |
Examples of foods high in essential amino acids (and arginine)
| Groceries | Histidine | Isoleucine * | Leucine * | Lysine | Methionine | Phenylalanine | Threonine | Tryptophan | Valin * | Arginine |
| Amaranth | 0.38 | 0.58 | 0.87 | 0.74 | 0.22 | 0.54 | 0.55 | 0.18 | 0.67 | 1.06 |
| Bush beans (raw) | 0.29 | 0.24 | 0.50 | 0.62 | 0.09 | 0.68 | 0.23 | 0.03 | 0.29 | 0.39 |
| Oats (raw) | 0.20 | 0.41 | 0.77 | 0.44 | 0.16 | 0.53 | 0.37 | 0.16 | 0.57 | 0.68 |
| hazelnut | 0.40 | 0.57 | 1.10 | 0.47 | 0.21 | 0.71 | 0.48 | 0.21 | 0.75 | 2.27 |
| Sunflower seeds | 0.69 | 1.13 | 1.70 | 0.99 | 0.56 | 1.28 | 0.95 | 0.37 | 1.33 | 2.46 |
| Lentils (raw) | 0.59 | 1.11 | 1.78 | 1.73 | 0.19 | 1.23 | 0.98 | 0.22 | 1.33 | 1.95 |
| Lupins | 1.03 | 1.61 | 2.74 | 1.93 | 0.25 | 1.43 | 1.33 | 0.28 | 1.51 | 3.87 |
| almond sweet | 0.53 | 0.91 | 1.51 | 0.60 | 0.27 | 1.20 | 0.63 | 0.17 | 1.18 | 2.84 |
| Soybeans (ripe, raw) | 1.09 | 1.97 | 3.30 | 2.70 | 0.54 | 2.12 | 1.76 | 0.59 | 2.02 | 3.15 |
| Tempeh (fermented soy) | 0.48 | 0.91 | 1.47 | 1.06 | 0.23 | 0.89 | 0.68 | 0.17 | 0.89 | 1.12 |
| tofu | 0.40 | 0.74 | 1.24 | 0.96 | 0.19 | 0.84 | 0.57 | 0.20 | 0.76 | 1.14 |
| egg | 0.26 | 0.73 | 0.99 | 0.70 | 0.35 | 0.63 | 0.56 | 0.18 | 0.88 | 0.70 |
| Parmesan | 0.92 | 1.78 | 2.89 | 2.18 | 0.71 | 1.41 | 1.26 | 0.40 | 1.94 | 1.01 |
| Yogurt 1.5% | 0.09 | 0.22 | 0.38 | 0.28 | 0.09 | 0.19 | 0.16 | 0.04 | 0.27 | 0.13 |
| Tuna (cooked) | 0.88 | 0.98 | 1.75 | 1.79 | 0.49 | 0.85 | 0.95 | 0.24 | 1.15 | 1.01 |
| Beef (cooked) | 0.49 | 0.75 | 1.22 | 1.27 | 0.37 | 0.62 | 0.67 | 0.16 | 0.82 | 0.91 |
| Recommendation per day (in g) | 0.7 | 1.4 | 2.7 | 2.1 | 0.7 | 1.75** | 1.0 | 0.28 | 1.8 | 1.5 |
Diagnostics “essential amino acids”
| substance | Normal values (mg/dl) | Key areas |
| Histidine | 1,226-1,877 | Hemoglobin formation, detoxification, precursor of histamine |
| Lysine | 2,266-4,020 | Cardiovascular protective factor, immune system, building block of carnitine |
| Threonine | 1,429-2,239 | Collagen building block, immune system, intestinal barrier |
| Phenylalanine | 0.760-2.973 | It has analgesic effects and is a precursor to tyrosine, thyroxine, and catecholamines. |
| Tryptophan | 0.694-1.838 | Blood pressure reduction, sleep promotion, immune system support |
| (Arginine) | 1,307-2,439 | Immune system, collagen synthesis, precursor of NO |
| Methionine | 0.373-0.731 | Methyl group donor, detoxification, immune system, redox system |
| Leucin | 1,377-2,637 | Reserve energy |
Suggestions for the approximate daily requirement of essential amino acids (in g)
| substance | Requirement |
| Isoleucine (VK) | 1.4 g |
CV = Branched-chain amino acids; SH = Sulfur-containing amino acids; AAS = Aromatic amino acids; SE = Semi-essential