Sulfur Containing Amino Acid Strengthen Cell Membranes
May 02, 2009 11:41 AM
Author: Darrell Miller (email@example.com)
Methionine is an essential amino acid, meaning that it is not synthesized by the body, and so has to be taken as part of your diet. It also contains sulfur, one of two sulfur-containing amino acids that can form proteins, the other being cysteine. It is a precursor for taurine, which is an aminosulphonic acid, and not strictly an amino acid, which together with cysteine supports the health of your cardiovascular system and helps to eliminate toxins from the body.
Maintenance of Cell Membranes
It is also an important intermediary in the maintenance of cell membranes. Phospholipids are fat-soluble components of the cell membrane, phosphatidylcholine being a very important example. Also known as lecithin, this substance is derived from choline, itself biosynthesized in a chemical pathway involving S-adenosylmethionine.
This substance is made in the body from ATP (adenosine triphosphate) and methionine with the help of the enzyme methionine adensosyltransferase. Known as SAM (or SAM-e), S-adenosylmethionine employs a number of metabolic pathways in its reaction, though generally aminopropylation, transmethylation and transsulfuration. These add aminopropyl, sulfo and methyl groups to a number of substances, the most common being the methylation of proteins, nucleic acids and lipids.
Phosphatidylcholine is produced by the enzyme-catalyzed sequential methylation of phosphatidylethanolamine, SAM donating the methyl groups. The maintenance of the integrity of the cellular membrane by phosphatidylcholine is critical to all of the basic processes in human biology, including communication between cells, flow of information and bioenergetics.
A by-product of this reaction is homocysteine, formed in the liver from the S-adenosylhomocysteine that SAM is changed to after donating methyl groups. Excess homocysteine in the blood can create the risk of myocardial infarction and cardiovascular disease. SAM is also of use in the treatment of depression and of arthritis.
Creatine is a substance well known to athletes as being useful in provide short-term energy for high-intensity training. Although available in the diet, about 50% creatine used by the body is biosynthesized from methionine and two other amino acids, glycine and arginine. It allows a burst of energy lasting about 10 seconds, carried out without the use of glycogen reserves or fatty tissue.
Glycine and arginine combine to release ornithine as a by-product, and form guanidino acetate. SAM donates a methyl group to the latter to form creatine, about 95% of which is then stored in the skeletal muscle tissue. The stored creatine phosphate has the effect of allowing the muscle cells to hold more water, which also enables an enhanced level of protein synthesis, and hence an increase in muscle bulk, which also results from the increased blood flow resulting from the short-term high-intensity exercise that creatine allows.
Creatine can also increase the levels of MRF4 (myogenic transcription factor), resulting in an increasing in the myonuclei provided by satellite cells to damaged muscle tissue, that not only repair damaged muscle fibers, but also increase their ability to grow.
Detoxification of the Liver
Substances that help the liver to process fats, or lipids, are known as lipotropic, and the important lipotropics in human biochemistry are imositol, betaine, choline and methionine. They prevent fat from accumulating in the liver, and methionine is also useful in its effect of glutathione. This is a substance that helps the liver to neutralize toxins, such as excessive doses of acetaminophen, and its supplies are regulated by methionine.
Methionine and Autism
Research into autism is closely studying the Methionine/Glutathione Transsulfuration Pathway. This pathway is a very important biochemical means of detoxification, whereby toxins are methylated and then excreted. This pathway seems to be disrupted in autistic individuals.
Not only that, but disruption can lead to oxidative stress which results in many health problems. An example of this is the build-up of the oxidant homocysteine when there is insufficient Vitamin B6 to convert it into cysteine. This has been discussed previously, and is discussed again below.
Although research is in its infancy, it appears that AIDS sufferers also have decreased levels of methionine in their blood. It is believed that the process of AIDS could be linked to this, particularly the dementia that can occur as a result of the deterioration of the nervous system.
It is also hoped that it can help with some symptoms of Parkinson's disease, and pancreatitis. Initial research into this use of methionine has been very promising, as are studies into its use for urinary tract infections. It appears to operate like cranberry in this respect, preventing bacteria from attaching to the cell walls and multiplying in the urinary tract.
Methionine is believed to be essential for the formation of collagen, and for healthy pliable skin, hair, nails and other forms of connective tissue. For this reason it is often used as a supplement for the treatment of arthritis, although an excess should be avoided for reasons discussed above. S-Adenosylmethionine generates homocysteine during the biosynthesis of phosphatidylcholine, and this can cause cardiovascular problems.
So stick to the recommended doses when you use methionine as a supplement. Used properly, and according to instructions, it offers many health benefits, and can also be used to bulk up your muscle tissue and give increased energy when you need it most.
Dietary sources include fish, eggs, lentils, onions, garlic, meat, seeds, spinach and yoghurt. A good supplement would be from 800mg - 1000mg per day, and is best taken along with a B vitamin complex, or at least folic acid and vitamins B6 and B12, in order to prevent the increased generation of homocysteine.
Methionine also promotes the excretion of estrogen, so is a possible supplement for women on oral contraceptives that lower the production of this hormone. The elderly might also benefit from a supplement although, if taken for any specific condition, your health professional should be consulted first, as they should be for any supplement.
Nevertheless, methionine is a very useful supplement, and can be taken to prevent a large number of conditions. Research is continuing on its effect on AIDS patients, and Parkinson's, and it is hopeful that it will one day be recommended to help people suffering from these conditions.