Glycine

Glycine is one of the 20 amino acids commonly found in proteins. Glycine is the only amino acid found in proteins that does not have two forms. Most proteins contain only small quantities of glycine. A notable exception is collagen, which contains about 35% glycine.
Glycine is not essential to the human diet, since it is biosynthesized in the body from the amino acid serine, which is in turn derived from 3-phosphoglycerate. In most organisms, the enzyme Serine hydroxymethyltransferase catalyses this transformation by removing one carbon atom; pyridoxal phosphate is also necessary.
In the liver of vertebrates, glycine synthesis is catalyzed by glycine synthase (also called glycine cleavage enzyme).
Glycine is a building block to numerous natural products. In multicellular organisms, D-Aminolevulinic acid, the key precursor to porphyrins, is biosynthesized from glycine and succinyl-CoA. Glycine provides the central C2N subunit of all purines.
Glycine is an inhibitory neurotransmitter in the central nervous system, especially in the spinal cord, brainstem, and retina.
Glycine is a sweet tasting, non-essential amino acid that was first isolated in 1820 from gelatin and is also found in good quantity in silk fibroin. This nonessential nutrient can be manufactured from serine and threonine, so dietary intake is not essential.
Glycine is required to build protein in the body and for synthesis of nucleic acids, the construction of RNA as well as DNA, bile acids and other amino acids in the body. It is further found to be useful in aiding the absorption of calcium in the body.


Glycine helps in retarding degeneration of muscles since it helps to supply extra creatine in the body.
Glycine is also found in fairly large amounts in the prostate fluid and may for this reason be important in prostate health.
Glycine is also used by the nervous system and its function as an inhibitory neurotransmitter makes it important to help prevent epileptic seizures, and glycine is also used in the treatment of manic depression and hyperactivity.
Few people are glycine deficient, in part because the body makes its own supply of the non-essential amino acids, and because it is abundant in food sources.
No clear toxicity has emerged from glycine studies, however individuals with kidney or liver disease should not consume high intakes of amino acids without consulting a health care professional.
In a study where men were given extra glycine over a period of time, it reduced the symptoms of prostatic hyperplasia.
If the amino acid serine is required in the body, it can be converted from glycine.
High protein food contains good amounts of glycine and is present in fish, meat, beans, and dairy products.