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Glycine

physical science Maturity 11-13 Next article →

Glycine is an organic compound with the chemical formula C2H5NO2. It is recognized as the simplest stable amino acid. Amino acids are the fundamental building blocks used to construct proteins in all forms of life.

Glycine-spin
Glycine-spin

Glycine is unique because it has a single hydrogen atom as its side chain. This tiny side chain makes glycine the only common amino acid that is not chiral. In chemistry, being non-chiral means the molecule is superimposable on its mirror image. This small size allows glycine to fit into very tight spaces within complex biological structures.

In the human body, glycine performs several vital mechanical roles. Because of its minimal structure, it is essential for forming certain protein shapes. It is especially important in collagen, a major structural protein. In collagen, glycine makes up about 35% of the amino acid content. This high concentration enables the tight coiling of the collagen triple helix.

Glycine-protonation-states-2D-skeletal
Glycine-protonation-states-2D-skeletal

Furthermore, glycine can disrupt the formation of alpha-helices in secondary protein structures. Instead, it encourages the formation of random coils.

Beyond structural support, glycine acts as an inhibitory neurotransmitter. This means it helps regulate signals within the central nervous system. It is particularly active in the spinal cord, the brainstem, and the retina. When glycine receptors are activated, chloride enters the neuron through ionotropic receptors. This process causes an inhibitory postsynaptic potential, or IPSP. This action helps balance motor and sensory signals. If these signals are disrupted, it can lead to severe neurological disorders. For example, the tetanus toxin causes spastic paralysis by blocking the release of glycine.

Glycine also serves as a key precursor for many other important biomolecules. It is used to synthesize porphyrins, which are necessary to form heme in the blood. It also provides the central C2N subunit for all purines. Purines are the building blocks used to construct DNA and RNA. In the liver of vertebrates, the enzyme glycine synthase helps catalyze its production. This process is reversible and involves molecules like carbon dioxide and ammonia. The body can also derive glycine from other substances like threonine, choline, or hydroxyproline.

Cu(gly)2(OH2)
Cu(gly)2(OH2)

The history of glycine discovery involves several important scientists. French chemist Henri Braconnot discovered it in 1820. He found it by hydrolyzing gelatin with sulfuric acid. He initially called the substance "sugar of gelatin." In 1838, Jean-Baptiste Boussingault proved that it contained nitrogen. In 1847, Eben Norton Horsford proposed the name "glycocoll." However, the Swedish chemist Berzelius suggested the name "glycine" only one year later. The name comes from the Greek word "glykys," which means sweet. This is why glycine is a white, sweet-tasting crystalline solid.

Industrial production of glycine is quite large. In the United States and Japan, about 15,000 tonnes are produced annually via Strecker amino acid synthesis. This is a main synthetic method used in those regions. In the United States, the market is divided into different grades. The United States Pharmacopeia, or USP, grade accounts for about 80 to 85 percent of the market. This high-quality grade is often used for medical purposes. Technical grade glycine is sold at a lower price for industrial uses, such as metal finishing.

Glycine is also used as a chemical feedstock in many industries. It acts as an intermediate in the manufacture of various products. For example, it is used to make the herbicide glyphosate. It is also used in the production of certain antibiotics, such as thiamphenicol. In laboratory settings, glycine is a significant component in protein analysis. It serves as a buffering agent in the SDS-PAGE method. This helps maintain the pH and prevents damage to samples during electrophoresis. Its versatility makes it useful in both biology and heavy industry.

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File:Glycine-spin.gif
Glycine-spin.gif
File:Glycine-protonation-states-2D-skeletal.png
Glycine-protonation-states-2D-skeletal.png
File:Cu(gly)2(OH2).png
Cu(gly)2(OH2).png
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