Protein - Amino Acids

AMINO ACIDS

Protein is made up of Amino Acids which are considered to be the building blocks of life. There are nine essential amino acids which must be obtained in the diet. In addition there are a further 13 amino acids present in protein which are considered non-essential as they can be synthesised by the body. There are also many other amino acids but they do not form parts of protein.

Research over recent years has shown that the human body has evolved to best utilise amino acids which are in dipeptide and tripeptide form (these are most commonly found in hydrolysates, ion exchanges and cross flow prepared whey proteins) which simply means two or three amino acids have been joined together. These are better absorbed, and retained, than both whole food proteins and free form amino acids.

There are a group of amino acids called Branched Chain Amino Acids (BCAA) which play an important role during exercise. They are the main amino acids to be sacrificed from muscle tissue during muscle catabolism. BCAA consist of three amino acids; leucine, Isoleucine, and Valine. The cause of this breakdown is that during exercise large amounts of the non-essential amino acids alanine and glutamine are used, in fact more than the body stores, and the deficit is made up by the body converting BCAA's into these two aminos.

To prevent this breakdown it has become common to try to raise blood levels of BCAA prior to exercise to reduce muscle breakdown. Supplementing with Glutamine directly after training then further reduces post exercise catabolism.

Glucogenic Amino Acids is a term used to describe the three amino acids threonine, glutamine and arginine. This term means that they lend themselves to glucose production, which is used for energy during exercise. Ample levels of these aminos may help prevent muscle breakdown, and has also been shown to increase feed efficiency in animals (ie grow more from the same amount of food).

Protein technologies have identified a group of amino acids called the Critical Cluster Amino Acids which play a big part in muscle sparing during dieting or intense exercise. This cluster consists of the three BCAA's along with Glutamine and Arginine which are two 'conditionally essential' amino acids. Around 45% of whey protein consists of the critical cluster aminos, with milk (casein) and soy protein isolate next in line at around 36%.

ESSENTIAL AMINO ACIDS

Histidine
This is a basic amino acid due to its aromatic nitrogen-heterocyclic imidazole side chain. It is biochemically metabolised into the neurotransmitter histimine.

Isoleucine
This amino acid has no other significant biological role than incorporation into proteins and enzymes where main purpose is to help dictate tertiary structure of macromolecules.

Leucine
This is a hydrophobic amino acid found as a structural element on the interior of proteins. It is the second most common amino acid found in proteins

Lysine
This amino acid is commonly found at the surface of proteins and is present in meat, fish, poultry and dairy.

Methionine
This amino acid helps to initiate translation of RNA by being the first amino acid incorporated into the N-terminal position of all proteins.

Phenylalanine
Plays a key role in the biosynthesis of amino acids and neurotransmitters.

Threonine
Plays an important role in Porphyrin metabolism.

Tryptophan
Is the biosynthetic precursor to the important neurotransmitter serotonin.

Valine
Determines the 3D structure of proteins due to its hydrophobic nature. Sources include soy flour, cottage cheese, fish, meat and vegetables.

NON-ESSENTIAL AMINO ACIDS

Alanine
Involved in the metabolism of tryptophan. One of the simplest amino acids most widely used in protein construction. It has little therapeutic role in humans however has been shown to have a cholesterol reducing effect in rats.

Arginine
A complex amino acid often found at the active catalytic site in proteins and enzymes. Is actually an essential amino acid during the juvenile period in humans. Natural sources include brown rice, nuts, raisins, and whole wheat.

Asparagine
A derivative of Aspartic Acid. Has an important role in the biosynthesis of proteins.

Aspartic Acid
This amino has a paramount role in metabolism during construction of other amino acids and biochemical's in the citric acid cycle.

Cysteine
Often involved in the three dimensional stability of proteins and critical to the metabolism of coenzyme A, biotin, lipoic acid, & glutathione.

Glutamic Acid
Negatively charged and therefore very polar and usually found on the outside of proteins where it is free to interact with intracellular surroundings.

Glutamine
Has an important role in cellular metabolism of animals and is the only amino acid with the ability to easily cross the barrier between blood and brain. It also has a central role in the regulation of bodily ammonia levels.

Glycine
This is the simplest amino acid and is essential for the biosynthesis of nucleic acids as well as bile acids & creatine phosphate. It is the second most common amino acid found in proteins which has the ability to inhibit neurotransmitter signals in the central nervous system.

Proline
This is a major component of the protein collagen, the connective tissue that binds and supports other tissues.

Serine
This amino has a major role in a variety of biosynthetic pathways including those involving pyrimidines, purines, & creatine.

Valine
Determines the three dimensional structure of proteins due to its hydrophobic nature. Sources include soy flour, cottage cheese, fish, meat and vegetables.