Glutamic Acid Definition

The amino acid glutamic acid (Glu or E) has an organic compound with the formula C5H9O4, and is a non-essential amino acid, which means the body can make it.

Under physiological conditions, the carboxyl group of glutamic acid has shed a proton, resulting in a negative charge. This amino acid is referred to as glutamate, and it is abundant in the human body.

As a building block, glutamic acid is essential for proteins. Glutamate is an essential neurotransmitter throughout the central nervous system and is also abundant in the brain. independent of its action as an amino acid.

Structure and Properties of Glutamic Acid

Glutamic acid has the chemical formula C5H9NO4 and is an amino acid. Either Glu or E are its symbols. It contains a carboxyl terminus, an amino terminus, and a lateral chain, much like all the other amino acids. A carboxylic acid group exists on the lateral chain of glutamic acid. The mRNA codons GAA and GAG, the genetic code, specify its incorporation into a polypeptide chain.

Glutamic acid, like all other amino acids (excluding glycine), comes in both L and D variants. The only difference between these stereoisomers is the spatial configuration of their atoms. In most cases, cells only contain the L-form. Except in a few rare circumstances, glutamic acid is usually always present in its L-form. For example, the D-form, many bacterial cell walls and liver cells contain this molecule.

Glutamate cannot penetrate the blood-brain barrier, so it must be generated in the brain even if it is supplied by food. It is made from the intermediate molecule-ketoglutarate, which is generated by the Krebs Cycle.

Glutamic Acid vs. Glutamate

Glutamate is produced when a hydrogen ion is lost from the carboxyl group of glutamic acid. The side chain of glutamic acid is CH2CH2COOH, while the side chain of glutamate is CH2CH2COOH. In summary, glutamate is the anion of glutamic acid. The terms are often interchanged.

Glutamic acid contains a pKa value of 4.1, which is a measure of an acid’s relative strength. A pKa value of 4.1 indicates that it sheds its positive charge and resides predominantly in its negatively charged form in settings where the pH is over 4.1.

Since the body’s environment (pH 7) encourages the discharge of positive charges, glutamic acid is almost always present as glutamate in the human body. As a consequence, it is classified as a polar, negatively charged, aliphatic amino acid under physiological circumstances.

Glutamic Acid vs. Glutamine

The amino acids glutamic acid and glutamine are commonly mistaken due to their similar names. The side chain of glutamine (Gln or Q)identical to the structure of glutamic acid, except if the carboxylic acid group has been replaced by an amide group (NH2).

The glutamate-glutamine cycle allows glutamine to be converted into glutamate in the central nervous system.

Umami Flavoring

Umami flavour is also caused by glutamic acid. This is the newest of the five tastes that have been categorised (the other flavours being salty, sweet, bitter, and sour). Umami is the Japanese word for “pleasantly savoury flavour.” Through glutamate receptors, we detect this flavour in meals rich in glutamates, like gravies, shellfish, yeast extract, and soy sauce. As a consequence, monosodium glutamate, a type of glutamate, is used as a taste enhancer (MSG).

Biological Activity of Glutamic Acid

Glutamate as a Neurotransmitter

Glutamic acid (particularly glutamate) is a neurotransmitter found in the central nervous system, as well as a protein-building ingredient. Glutamate is the primary excitatory neurotransmitter in the brain and nerve tissue, where it is plentiful.

Neurotransmitters are biological substances that operate as signalling molecules in the neurological system. In addition to glutamate, important neurotransmitters include acetylcholine, adrenaline, and dopamine.

Glutamate exerts its effects via binding to and activating receptors, mostly found on the cell membranes of neurons as well as astrocytes. The four types of receptors are AMPA, kainate, NMDA, and metabotropic receptors.

When glutamate attaches to its receptors as an excitatory neurotransmitter, it enhances the possibility of the neuron firing an action potential. Action potentials, often known as “nerve impulses,” are the means through which excitatory neurons communicate with one another via delivering signals.

Glutamate is held in vesicles at chemical synapses. Exocytosis releases glutamate into the synaptic cleft. If a neural impulse approaches a synapse, it may stimulate glutamate receptors on the following cell.

Ionotropic receptors, such as AMPA, kainate, and NMDA, when active, these channels allow ions to pass across the membrane. Metabotropic receptors become highly varied, and they often work via second messenger signalling.

The neurotransmitter function of glutamate is crucial for synaptic plasticity, which is required for memory and learning.

Glutamic Acid Decarboxylase

The enzyme glutamic acid decarboxylase catalyses the transformation of glutamate to gamma-aminobutyric acid (GABA). Therefore, glutamate functions as a forerunner to GABA. The nervous system’s primary inhibitory neurotransmitter

GABA stimulates GABA receptors by binding to them. GABA works as an inhibitory neurotransmitter by binding to this receptor, lowering the likelihood that a neuron may fire an action potential. Because it suppresses cell firing, increasing GABA receptor activation may have a sedative effect. Benzodiazepines and alcohol, for example, constantly bind to and activate GABA receptors.

Clinical Relevance

Impaired glutamate transmission in the brain has been linked to a variety of diseases.

Neurodegenerative Disease

The majority of central nervous system processes need glutamate. Prolonged glutamate stimulation of neurons has been related to central nervous system degenerative illnesses such as motor neuron disease, Huntington’s disease, and Alzheimer’s disease. This is the result of glutamate poisoning, also known as excitotoxicity, which may induce brain cell destruction and chronic diseases of the nervous system.

Psychiatric Disorders

Excess glutamate has previously been linked to mental disorders, including severe depressive disorder, schizophrenia, and bipolar disorder. Currently, pharmacological drugs (such as ketamine) that impact the glutamate system are being evaluated in medical trials for the therapy of these kinds of mental disorders.

Substance Abuse

Additionally, glutamate contributes to the development and maintenance of dependence. Its function in cognitive processes including reinforcement, sensitization, habit acquisition and reinforcement, conditioning, desire, and relapse has contributed to this. As a result, glutamatergic drugs are being studied as a possible therapy for drug-taking behaviours, withdrawal symptoms, and relapse prevention.

References

• Garrett, R. H., & Grisham, C. . (2016). Biochemistry 6th edition. In Biochemistry 6th edition.
• Glutamic acid | C5H9NO4 – PubChem. Retrieved June 9, 2020, from https://pubchem.ncbi.nlm.nih.gov/compound/Glutamic-acid
• Schaeffer, E., & Duplantier, A. (2010). Glutamate and Neurodegenerative Disease. https://doi.org/10.1007/7355_2010_11
• Stallard, C. N., & Saadabadi, A. (2019). Biochemistry, Glutamate. In StatPearls. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/30725952