Amino Acids: Protein Synthesis & Other Functions
Synthesis of Protein Needs Essential and Non-Essential Amino Acids
Dec 16, 2008
Amino acids are the building blocks for proteins. Enzymes, hormones, neurotransmitters, connective tissue, cell membranes, blood cells, for example, are all proteins and require amino acids for their synthesis. Additionally, many amino acids have other roles such as being substrates for energy production.
Regular consumption of essential amino acids is necessary; the body cannot produce them. However, the body can produce non-essential amino acids.
Essential Amino Acids and Functions
Histidine—a non-essential amino acid in adults but may be required in the diet of infants; therefore classed as conditionally essential. Histidine is a precursor to an acid that protects the skin from UV radiation, histamine, and carnosine, which is involved in muscle contraction. Histidine stimulates gastric juices and is involved in connective tissue production and haemoglobin formation.
Lysine—an essential amino acid. Lysine is important for connective tissue such as collagen and elastin and carnitine synthesis. It is essential for cell division.
Methionine—an essential sulphur containing amino acid. Methionine is required for the synthesis, utilisation or activation of other substances, such as neurotransmitters (acetylcholine), hormones (adrenalin), the antioxidant glutathione, other nutrients (selenium, CoQ10, vitamin B12 and folic acid) and nucleic acids.
Phenylalanine— an essential amino acid and major precursor to tyrosine. It stimulates production of some hormones and affecting gut function (cholecystokinin and gastrin).
Threonine— an essential amino acid that can produce energy, has immune properties; needed for connective tissue integrity, and a precursor of serine and glycine.
Tryptophan—an essential amino acid and precursor for melatonin, serotonin and niacin (vitamin B3).
The branched chain amino acids: Leucine, Isoleucine, and Valine—make up 35% of the muscle proteins and 50% of the dietary protein amino acids. They are specifically for protein synthesis. The main site of breakdown for branched chain amino acids is the skeletal muscle.
Non-Essential Amino Acids and Functions
Alanine— a non-essential amino acid produced from pyruvic acid and glutamic acid. Alanine is concentrated in connective tissue proteins such as collagen and is required for the use of amino acids as energy for muscles.
Arginine—a semi-essential amino acid produced from ornithine. In infants and young children, the body cannot meet the demands and in this situation it is essential. It is beneficial for immunity, DNA production, detoxification, hormone secretion and precursor to nitric oxide.
Aspartic acid— a non-essential amino acid produced from glutamic acid. It can produce energy, is a precursor to asparagine (a non essential amino acid) and DNA and RNA and an active part in a number of enzyme systems.
Carnitine—a non-essential amino acid produced from lysine. Carnitine transports fat from the cells for the production of energy. It is used in sporting activities to increase maximal aerobic output.
Cysteine/Cystine—a non-essential sulphur containing amino acid. Cysteine is part of the structure of the powerful antioxidant, glutathione. Methionine and serine produce cysteine and it is a part of many enzyme systems.
Glycine— a non-essential amino acid produced from serine. Glycine is also part of the structure of glutathione. Glycine is needed for the synthesis of the proteins RNA and DNA, pigments in haemoglobin and cytochromes, and for liver detoxification.
Glutamic Acid—a non-essential amino acid produced from alpha ketoglutarate and ammonia. It is part of glutathione and a precursor for proline, ornithine and arginine and the neurotransmitter GABA.
Glutamine— a non-essential amino acid but has been classed as a conditionally essential amino acid as the body is not able to produce enough in times of physiological stress. Glutamine has many important functions within the body including a vital energy source for the intestinal cells and precursor of glutathione production.
Inosine— a non-essential amino acid produced from adenosine. It is an important precursor to RNA, DNA and the energy molecule ATP.
Ornithine— a non-essential amino acid produced from glutamic acid. It is involved in ammonia detoxification, is required for sperm production, immune health and a precursor to arginine.
Proline— a non-essential amino acid produced from glutamic acid. It can provide energy and is a major component of the connective tissue; collagen and elastin.
Serine— a non-essential amino acid. It is required for glycine production, iron absorption, and as a constituent of the cell membranes.
Taurine— a non-essential sulphur containing amino acid produced from cysteine. Taurine assists in fat metabolism and removal of cholesterol by-products from the blood. It is an antioxidant with neurotransmitter properties. It is also involved in detoxification, membrane stabilisation and cellular calcium regulation.
Tyrosine— a non-essential amino acid produced from phenylalanine. Tyrosine is a precursor for neurotransmitters and hormones: dopamine, noradrenalin, adrenalin, thyroxine, and melanin.
References:
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