Generalities and Characteristics
There glycine (abbreviated Gly or G., brute formula NH2CH2COOH) is the smallest of the 20 ordinary amino acids (the one with the lowest molecular weight among the amino acids most present in proteins).
In fact, the
Crystallized glycine is solid, colorless and sweet in taste.
Glycine in Food
Glycine is an almost ubiquitous protein element, albeit in not very high percentages; being part of the collagen, present in connective tissues and epithelia, most meat foods should contain a good amount of it. Furthermore, the glycine content also appears significant in various products of plant origin.
According to the nutritional tables consulted, the 5 foods richest in glycine are: whitefish (4.4g / 100g), soy protein, spirulina algae, cod and egg white powder.
Soy (Glycine max) is one of the foods with the highest Glycine content
Since these are not ordinary foods, we also mention the foods richest in glycine among the most consumed: pork belly, mortadella, brisket, cooked cuttlefish, cooked chicken, veal rump, cooked octopus and pumpkin seeds (the latter 1, 8g / 100g).
Glycine Food Additive
Glycine is also a food additive for foods intended for human and animal nutrition.
In particular, glycine and its sodium salt are used as flavor enhancers (E640) and sweeteners, or as enhancers of pharmacological absorption.
Many dietary supplements and protein drinks contain added glycine.
Glycine and Aging
Topical treatment with glycine can help reverse the defects associated with the aging of human fibroblasts (cells responsible for the production of collagen).
It was recently discovered that the two genes CGAT and SHMT2 regulate mitochondrial activity and influence its deterioration.
In a study carried out in vitro for 10 days, the addition of glycine to fibroblasts (obtained from cells belonging to a 97-year-old human being) resulted in the restoration of mitochondrial function and of the fibroblasts themselves.
In practice, by modifying the regulation of these genes by administering glycine, the researchers were able to restore the mitochondrial function of the fibroblasts, to the benefit of collagen synthesis.
Medical Applications of Glycine
A 2014 article noted that glycine can improve sleep quality.
The reference was made to a study in which, in vivo and in humans, the administration of 3g of glycine before bedtime induced an improvement in rest.
Glycine has also been successfully tested in the adjuvant treatment supplement for schizophrenia.
Glycine: Cosmetics and Other Uses
Glycine is used as a buffer element in some products such as: antacids, analgesics, antiperspirants (armpit deodorants), cosmetics and toiletries. For more information, see the article: Glycine in Cosmetics.
The use of glycine also extends to other areas, such as that of foam, fertilizers and metal complexing agents.
Glycine, Drugs and Technical Use
Glycine is sold in two types and for two purposes: "pharmacological" and "technical".
Most of the glycine is produced as a pharmacological material and, to get an idea of the overall market, just think that its sales represent about 80-85% of the total trade (value referred to the US market).
Pharmaceutical glycine is produced for many applications; the one that requires the highest level of purity is intended for intravenous injections.
Conversely, technical-grade glycine does not have to meet any purity requirements. It is mainly sold for use in industrial applications; for example, as a complexing agent in metal finishing. The price of that for technical use is always lower than that of pharmaceutical glycine.
Functions of Glycine in the Body
The main function of glycine is the plastic one in protein synthesis, in particular in the "helical association with"hydroxyproline to form collagen. This amino acid is also an intrinsic element of many natural products.
Glycine represents a biosynthetic intermediate of porphyrins. In addition, it provides the central sub-unit of all purines.
Glycine is an inhibitory neurotransmitter of the central nervous system (CNS), particularly of the spinal cord and brain stem (as well as the retina). When the ionotropic glycine receptors are activated, an inhibitory postsynaptic potential occurs.
There strychnine and the bicuculline they are glycine receptor antagonists; the first of the two is a toxic alkaloid, or a poison.
On the other hand, glycine is also a glutamate co-agonist for NMDA receptors, therefore it also plays an excitatory role.
The LD50 (mean lethal dose) of glycine is 7,930 mg / kg in rats (orally) and usually causes death by hyperexcitability.
Glycine metabolism
Synthesis: glycine is not an essential amino acid and in addition to finding it in the diet, the body is able to synthesize it from serine (in turn produced by 3-phosphoglycerate).
- In most animal organisms, this transformation is mediated by the catalase enzyme serine hydroxymethyltransferase, through the cofactor pyridoxal phosphate.
- In the liver of vertebrates, the synthesis of glycine is catalyzed by the enzyme glycine dehydrogenase (a synthase also called enzyme cleavage enzyme) and the conversion is easily reversible.
- Only small amounts of glycine are present in most proteins, with the exception of collagen, which contains as much as 35% of this amino acid.
Degradation: glycine can be degraded through three pathways.
- The predominant one in humans involves the intervention of the enzyme glycine decarboxylase.
- In the second route, glycine is degraded in two steps; the first is the exact opposite of the synthesis, with the intervention of serine hydroxymethyltransferase, while the second involves the conversion into pyruvate by means of serine dehydratase.
- In the third degradation pathway of glycine, it is converted into glyoxylate by the D amino acid oxidase, subsequently oxidized by hepatic lactate dehydrogenase in oxalate.
The half-life of glycine and its elimination from the body varies significantly by concentration; it should be between 0.5 and 4.0 hours.
