Proline

Some important facts about Proline:
L-Proline is one of the twenty proteinogenic units which are used in living organisms as the building blocks of proteins. The other nineteen units are all primary amino acids, but due to the cyclic binding of the three-carbon side chain to the nitrogen of the backbone, proline lacks a primary amine group (-NH2). The nitrogen in proline is properly referred to as a secondary amine. Proline is sometimes called an imino acid, although the IUPAC definition of an imine requires a carbon-nitrogen double bond. In biological terminology, however, the category "amino acids" is generally taken to include proline.
1. Proline is one of the cyclic aliphatic amino acids that is a major component of the protein collagen, the connective tissue structure that binds and supports all other tissues.
2. Proline is synthesized from glutamic acid prior to its incorporation into pro-collagen during messenger RNA translation. After the pro-collagen protein is synthesized, it is converted by posttranslational modification into hydroxyproline. On a molar basis proline is incorporated into protein at a rate of 4.2 percent with respect to other amino acids.
3. Meat, dairy, and eggs are the best natural sources of proline; vegetarians or those with a low-protein diet should seriously consider a combination amino acid supplement containing, among other amino acids, proline. Proline supplements are available in stand-alone capsules and tablets, but this amino acid is also often included in supplements marketed for treatment of specific conditions, such as herpes (in combination with lysine), arthritis, or back pain, or in supplements or sports drinks marketed for body builders and athletes.
4. Proline may be in supplements used to promote cardiovascular health, usually in combination with vitamin C. The recommended therapeutic dose is between 500 milligrams and 1,000 milligrams daily, in combination with vitamin C.
5. People with liver or kidney disease should not take this or any other amino acid supplement without first consulting their physician. Getting too much of any one amino acid can throw the citric acid cycle out of balance, which makes the liver and kidneys work harder to eliminate toxins.

Use of proline:
1. Proline helps the body break down proteins for use in creating healthy cells in the body. It is absolutely essential to the development and maintenance of healthy skin and connective tissues, especially at the site of traumatic tissue injury.
2. Proline and lysine (another one of the amino acids that is important to protein synthesis) are both needed to make hydroxyproline and hydroxylysine, two amino acids that form collagen. Collagen helps to heal cartilage and to cushion the joints and vertebrae. For this reason, proline supplementation may prove beneficial for treatment of conditions such as osteoarthritis, persistent soft tissue strains, and chronic back pain.
3. The body needs proline to maintain muscle tissue as well. Decreases in proline levels have been noted in prolonged endurance runners and others following prolonged exercise. Serious athletes that subject their body to routine, rigorous workouts may want to take a supplement containing proline in order to avoid loosing muscle mass-the body begins to cannibalize its muscle for energy when glucose supplies run low.
4. The body makes proline from glutamic acid, and deficiency is rare in healthy individuals with a healthy diet. However, people recovering from traumatic injury, particularly skin injuries such as severe burns, may want to supplement this amino acid.
5. Proline is one of the main components of collagen. Collagen fibres are found in the tendons, ligaments and connective tissues of the body. Proline also promotes the formation of bone, skin and cartilage and it is extremely important for the proper functioning of joints and tendons, also helps maintain and strengthen heart muscles and is helpful in tissue repair after injury, or for any type of wound healing. Proline is also involved in energy production.
6. Proline helps the body break down proteins for use in creating healthy cells in the body. It is absolutely essential to the development and maintenance of healthy skin and connective tissues, especially at the site of traumatic tissue injury.
7. People with pain caused by insufficient cartilage or collagen formation could benefit from extra proline in their diet as well.

Properties:
Proline shares many properties with the aliphatic group.
1. Proline is formally NOT an amino acid, but an imino acid. Nonetheless, it is called an amino acid. The primary amine on the a carbon of glutamate semialdehyde forms a Schiff base with the aldehyde which is then reduced, yielding proline.
2. When proline is in a peptide bond, it does not have a hydrogen on the a amino group, so it cannot donate a hydrogen bond to stabilize an a helix or a ß sheet. It is often said, inaccurately, that proline cannot exist in an a helix. When proline is found in an a helix, the helix will have a slight bend due to the lack of the hydrogen bond.
3. Proline is often found at the end of a helix or in turns or loops. Unlike other amino acids which exist almost exclusively in the trans- form in polypeptides, proline can exist in the cis-configuration in peptides. The cis and trans forms are nearly isoenergetic. The cis/trans isomerization can play an important role in the folding of proteins and will be discussed more in that context.
4. The distinctive cyclic structure of proline's side chain locks its f backbone dihedral angle at approximately -75°, giving proline an exceptional conformational rigidity compared to other amino acids. Hence, proline loses less conformational entropy upon folding, which may account for its higher prevalence in the proteins of thermophilic organisms.
5. Proline acts as a structural disruptor in the middle of regular secondary structure elements such as alpha helices and beta sheets; however, proline is commonly found as the first residue of an alpha helix and also in the edge strands of beta sheets.
6. Proline is also commonly found in turns, which may account for the curious fact that proline is usually solvent-exposed, despite having a completely aliphatic side chain.
7. Because proline lacks a hydrogen on the amide group, it cannot act as a hydrogen bond donor, only as a hydrogen bond acceptor.
8. Multiple prolines and/or hydroxyprolines in a row can create a polyproline helix, the predominant secondary structure in collagen. The hydroxylation of proline (or other additions of electron-withdrawing substituents such as fluorine) increases the conformational stability of collagen significantly. Hence, the hydroxylation of proline is a critical biochemical process for maintaining the connective tissue of higher organisms. Severe diseases such as scurvy can result from defects in this hydroxylation, e.g., mutations in the enzyme prolyl hydroxylase or lack of the necessary ascorbate (vitamin C) cofactor.

Deficiency symptomsof proline:
Proline is a nonessential amino acid. The body makes proline from glutamic acid, and deficiency is rare in healthy individuals with a healthy diet.

Symptoms of high intake:
People with liver or kidney disease should not take this or any other amino acid supplement without first consulting their physician. Getting too much of any one amino acid can throw the citric acid cycle out of balance, which makes the liver and kidneys work harder to eliminate toxins.

Daily requirement:
The recommended therapeutic dose is between 500 milligrams and 1,000 milligrams daily, in combination with vitamin C.

Sources of proline:
Meat, dairy, and eggs are the best natural sources of proline; vegetarians or those with a low-protein diet should seriously consider a combination amino acid supplement containing, among other amino acids, proline.

Who need more?
People recovering from traumatic injury, particularly skin injuries such as severe burns, may want to supplement this amino acid. People with pain caused by insufficient cartilage or collagen formation could benefit from extra proline in their diet as well. Proline may be in supplements used to promote cardiovascular health, usually in combination with vitamin C. Decreases in proline levels have been noted in prolonged endurance runners and others following prolonged exercise. Serious athletes that subject their body to routine, rigorous workouts may want to take a supplement containing proline in order to avoid loosing muscle mass-the body begins to cannibalize its muscle for energy when glucose supplies run low.