Amino Acids & L-glutathione

Amino acids are nitrogen-containing molecules that perform a variety of functions in your body. Their most familiar role is in the synthesis of proteins, which form the structural basis for your connective tissues, organs, muscles and skin. Proteins also serve as functional molecules, such as enzymes, antibodies, hemoglobin and hormones. Amino acids provide the precursors for non-protein molecules, too, such as neurotransmitters, vitamins and antioxidants. L-glutathione, or GSH, is an important antioxidant constructed from three amino acids: cysteine, glutamic acid and glycine.

Synthesis

Although GSH is not an essential nutrient -- it can be manufactured within your cells -- its synthesis depends upon adequate supplies of its constituent amino acids, especially cysteine. According to Dr. Elson Haas, author of "Staying Healthy with Nutrition," when GSH is in low supply, it is usually due to a lack of cysteine. Cysteine itself is produced from the essential amino acid methionine, but this process is complicated and requires several vitamins and serine, yet another amino acid.

Antioxidant

Exposure to environmental toxins, pollutants and radiation induces the formation of toxic free radicals in your cells and tissues. In addition, normal cellular metabolism generates reactive substances, such as peroxides, that can damage nearby proteins, enzymes, chromosomes and cell membranes. By donating its electrons to free radicals and other reactive molecules, GSH effectively converts them to harmless compounds which can then be removed from your tissues. During this reaction, GSH itself is oxidized, but it is quickly converted back to its original form by the enzyme glutathione reductase.

Detoxification

The amino acid-glutathione relationship becomes particularly important when you are exposed to increased levels of toxins or pollutants, such as industrial chemicals, dietary contaminants or medications. Your body must detoxify these agents to prevent them from causing tissue injury, and GSH is a chief participant in this process. According to an October 2009 review in "The FASEB Journal," a group of enzymes called glutathione-S-transferases "conjugate" GSH with toxic compounds within your cells, facilitating their export and elimination. As GSH is also eliminated during this process, a continual supply of cysteine, glycine and glutamic acid is needed to replenish GSH.

Considerations

Glycine, glutamic acid and cysteine are nonessential amino acids, because all three can be manufactured in your body from other substances. Likewise, L-glutathione is not considered an essential nutrient. However, during periods of increased oxidative stress -- illness, exercise, surgery or exposure to toxins or medications -- your need for additional L-glutathione prompts a need for higher concentrations of its amino acid precursors. Cysteine is most likely to be the limiting factor in L-glutathione synthesis, and supplementation with 250 to 750 mg of cysteine daily might help to ensure adequate L-glutathione levels. Ask your doctor if amino acid supplements are appropriate for you.