Glycine is an amino acid that has many functions. It can be a neurotransmitter, it can inhibit the release of neurotransmitters, it can act as a buffer molecule in neurons, and it might also be an important regulator of glutamate receptor density. In addition to being found in proteins, glycine is also important for glucose homeostasis and cellular detoxification.
There are a number of articles on the site discussing glycine's role in diabetes prevention as well as its use to prevent seizures. Glycine has been shown to regulate blood pressure and plays an important role in physical recovery from injury or surgery by helping with cell repair and collagen production. Glycine is also involved in the detoxification process.
Numerous studies have shown that glycine plays a major role in sleep regulation. Interestingly, it appears to induce sleep by blocking N-methyl-D-aspartate (NMDA) receptors – the very receptors that are activated by the excitatory neurotransmitter, glutamate! Glutamate is one of the primary excitatory neurotransmitters found in the brain and plays an important role in learning, memory and cognition. The NMDA receptor is made up of two NR1 subunits and two NR2 subunits. It's the NR2 subunits that glycine binds to. When glycine binds to the NMDA receptor, it prevents glutamate from binding to these sites, thereby reducing the activity of this receptor.
Glycine and Hypoglycemia
The results of a study published in November 2013 indicate that glycine can help prevent hypoglycemia by blocking the release of hormones from the pancreas. The study involved rats and was conducted at Barrow Neurological Institute (Barrow) in Phoenix, AZ. According to an article on Science Daily: "Normally blood sugar increases after a meal and triggers the release of hormones from the pancreas (insulin and glucagon). These hormones signal to the liver to start breaking down glycogen and converting it to glucose (sugar). But in this study, researchers found that glycine blocked the release of the two hormones and therefore prevented sugar from being released into the bloodstream" (Science Daily, November 6, 2013).
Glycine and Lipid Metabolism
A 2012 study by Bhasin et al., published in Molecular Pharmacology (Bhasin et al., 2012), found that glycine protected against lipid peroxidation in macrophages resulting from oxidative stress. The diet used in the study contained a high amount of fat. Glycine is one of the simplest amino acids and is a common constituent in protein. It also has some important roles in human metabolism.
Glycine helps regulate acid-base balance by acting as an acid: it can donate a hydrogen ion to help regulate pH. Glycine may also be converted into serine, which can be converted to glucose; or into ornithine and then argininosuccinate, both of which are involved in urea synthesis. Glycines are degraded by nerve cells to fuel synthesis of the important neurotransmitter acetylcholine; glycinergic neurons use this process for energy production.
The most common side-chain functional group in glycine is–OH, although two other common amino acid side chains are –NH and –NHR. The(–NHR) group is usually found attached to the terminus of a peptide or protein. Glycine can also form a covalent (R) bond with other molecules, such as esters or amides.
Glycine occurs naturally in proteins at concentrations ranging from about 0.3% to around 5%, but it is not essential for normal growth or life processes because plants and animals synthesize it from ethanolamine using glutamic acid as a precursor.