Tag Archives: sulfur-containing amino acids

Amino Acids and Gut Health – Glutamine and Other Aminos

There are a number of amino acids that affect the intestines and are necessary for proper functioning. Several amino acids and gut health are connected; in particular, glutamine (which I will cover more in-depth below), arginine, glutamate, glycine, threonine, lysine, as well as sulfur-containing aminos. These amino acids and gut functioning are important because they act as fuels for mucosa in the small intestine, and also for the synthesis of nitric oxide (NO), intestinal proteins, polyamines, and other products that are necessary for health. Amino acids come from protein foods like meats, fish, and eggs, or from taking supplements. 

What this means—according to a study by WW Wang, SY Quiao, and DF Li—is that glutamine and the other amino acids and gut-promoting effects from these aminos are not only “critical for the absorption of nutrients” but also are required for the “gut integrity, growth, and health in animals and humans.”

The researchers show that amino acids and gut health, in particular, indicate both trophic and cytoprotective effects. Trophic means relating to feeding and nutrition, and cytoprotective means it protects the cells from noxious chemicals and other things that would otherwise bother the intestinal tract and cause health problems.

Amino acids and gut health includes glutamine

According to the researchers RR van der Hulst, MF von Meyenfeldt, and PB Soeters, one of the essential amino acids and gut nutrients is glutamine. This non-essential amino acid (meaning your body can produce it, even though you can also get it through protein foods and supplements), is “an important nutrient for rapidly dividing cells such as cells from the immune system and the gut.”

There are a few conditions that can also cause a lack of glutamine, which can, according to the scientists, result in “functional disturbances of the immune system and/or the gut. Glutamine is produced mainly by the muscle tissue. A decrease in muscle mass during nutritional depletion may result in decreased glutamine production capacity. Furthermore during critical illness, there is an increased demand for glutamine probably as a result of an increased utilization by the immune system.”

Additionally, glutamine as one of the amino acids and gut nutritives, is important because it prevents toxins and/or bacteria from migrating from the gut lumen (the hollow part of the intestine) into the circulation of the system. Not having enough glutamine can deteriorate this barrier within the intestine and would, in this case, require supplementation of glutamine.

Lastly, glutamine (or other amino acids and gut health) may need to be supplemented in case of nutritional depletion, parenteral nutrition, or even critical illness.

Reference:

http://www.ncbi.nlm.nih.gov/pubmed/18670730

http://www.ncbi.nlm.nih.gov/pubmed/8974125

Sulfur-Containing Amino Acids Cysteine and Methionine

The two main sulfur-containing amino acids are cysteine and methionine; however, there are other sulfur-containing amino acids as well. Both cysteine and methionine are nonpolar as well as hydrophobic, with methionine being extremely hydrophobic as far as amino acids go. Methionine is also found inside proteins, and cysteine is often found there too. There are some other fascinating things about these two (and other) sulfur-containing amino acids.

Aside from methionine and cysteine being most popularly known, other commonly known sulfur-containing amino acids include homocysteine and taurine. The last two are not incorporated into proteins, however. According to the authors at the Journal of Nutrition (JN), the “difference accounts for some of the distinctive properties of the sulfur-containing amino acids. Methionine is the initiating amino acid in the synthesis of virtually all eukaryotic proteins … [and if] exposed, are susceptible to oxidative damage. Cysteine, by virtue of its ability to form disulfide bonds, plays a crucial role in protein structure and in protein-folding pathways.”

The authors of JN discuss a number of these sulfur-containing amino acids—methionine, cysteine, taurine, homocysteine, and the lesser known S-adenosylmethionine.

Importance of sulfur-containing amino acids

Although cysteine and methionine are the primary sulfur-containing amino acids due to being two of the 22 common amino acids that are incorporated within proteins, both taurine and homocysteine are also important for physiological function. So why is sulfur in amino acids since most aminos are made of carbon, oxygen, hydrogen, and nitrogen? Because, says JN, oxygen and sulfur both belong to ‘Group 6’ of the Periodic Table of Elements, so are “capable of making similar covalent linkages” with a critical difference that sulfur has a low electronegativity (oxygen has the second lowest electronegativity). So if oxygen replaces the sulfur it would “result in a much less hydrophobic amino acid.”

Furthermore, substituting oxygen for sulfur—causing oxidation—in sulfur-containing amino acids (including in the more rare S-adenosylmethionine) can have effects in methionine residues where the surface is exposed, causing an oxidation-reduction cycle, imparing the activity of “methionine sulfoxide reductase and the subsequent accumulation of methionine sulfoxide residues [that] are associated with age-related diseases, neurodegeneration, and shorter lifespan.”

Lastly taurine, as one of the more remarkable sulfur-containing amino acids, has very high concentrations within muscle tissues and utilizes a wide variety of functions. Taurine is, says JN, the “most abundant free amino acid in animal tissues [even though it] accounts for only 3% of the free amino acid pool in plasma, it accounts for 25%, 50%, 53%, and 19%, respectively, of this pool in liver, kidney, muscle, and brain.” It is also one of the most necessary sulfur-containing amino acids for cats and results retinal degeneration in kittens if the mothers are not fed a taurine-rich diet. Taurine is also found in human mother’s milk and is added to many infant formulas because it helps with eyesight.

So all in all, sufur-containing amino acids are necessary for proper health of both animals and humans in the proper biological functioning and growth, as well being associated with some diseases and anti-aging and neurological issues.

Reference:

http://jn.nutrition.org/content/136/6/1636S.full