[Chemistry Class Notes] Non-Standard Amino Acids Pdf for Exam

Non- amino acids are organic molecules that are not composed of amino acids. There are many different types of non-amino acids, and they can be found in both natural and synthetic forms. Some of the most common non-amino acids include sugars, lipids, and nucleic acids. Non-amino acids are used in various areas of the plant and even humans for different purposes. For example, when the non-amino acid ribonucleic acid (RNA) is combined with DNA, it becomes messenger RNA (mRNA), which serves as a transcriptional control protein that works in the nucleus of a cell. The cell can then use this messenger RNA to produce proteins and the cell is thus able to function. The same concept applies to amino acids in which some of the non-amino acids can be utilized as a building block and others will be degraded. The role of the non-amino acids can be diverse. Some of them will be used in metabolic processes. However, some of them may not be used for a long time and then will become no longer usable. In addition to the need for amino acids in biological processes, there are also non-amino acids that must be present in a certain amount. 

These non-amino acids are known as essential amino acids. The different types of non-amino acids are not the same, and they are not all manufactured the same way. For example, there are certain metabolic processes that do not require the presence of certain non-amino acids. Examples of non-essential amino acids include hydroxyproline, glycine, serine, threonine, lysine, arginine, and aspartic acid. In cases of long-term starvation, the body may use its protein stores and depleted non-essential amino acids will be used instead of the essential ones. To maintain a healthy body and to prevent many health problems, it is very important that we consume certain essential amino acids on a regular basis. Supplements With Essential Amino Acids for Health The body needs the essential amino acids in different quantities and it is not possible to provide them through supplements. When the body is not supplied with the required amount of essential amino acids, these amino acids will be converted into other compounds, which are called by-products. Some of these by-products are toxic. For example, the body makes some proteins that are harmful to the liver. The main amino acids that the body needs are listed below. We should remember, however, that the recommended daily amount of each of these amino acids depends on an individual’s gender, age, and weight.

Non-Standard Amino Acids Definition

Non-standard amino acids are amino acids that are considered to be chemically modified after they are incorporated into a protein; this is known as post-translational modification. This type of amino acid is known to be found in various living organisms but does not occur in all proteins. They are not found in the genetic code of any organism. This type of amino acid can get created naturally as well as artificially in the laboratory. They are known to be present in meteorites and are capable of getting used in prebiotic experiments.

()

Standard and Non-Standard Amino Acids

Amino acids are considered to be molecules that are characterized by the presence of an amino group and a carboxylic group in the molecular structure of the compounds. Hence, these molecules are termed amino acids. The main function of an amino acid is to act as a manometer for the purpose of the synthesis of proteins and peptides. From all the amino acids that exist naturally, there is a set of 20 amino acids which are termed standard amino acids. These standard amino acids serve as building blocks for the proteins that are produced in a living organism. These acids are studied widely all over the world. The standard amino acids are:

• Glycine

• Alanine

• Proline

• Valine

• Leucine

• Isoleucine

• Methionine

• Phenylalanine

• Tyrosine

• Tryptophan

• Serine

• Threonine

• Cysteine

• Asparagine

• Glutamine

• Lysine

• Arginine

• Histidine

• Aspartate

• Glutamate

Besides standard amino acids, there are some acids that are found in some proteins and are known as non-standard amino acids. The acids have a different composition that doesn’t match the composition of standard amino acids. They are known for presenting different physicochemical properties. Therefore, when it becomes necessary to introduce a local in a particular protein with specific properties, and it can’t get incorporated by the standard amino acids, then the non-standard amino acids come into the scene, and they are used for incorporation. So it is clear that the only difference between standard and non-standard amino acids is their composition.

Some examples of non-standard amino acids are:

• Cystine, desmosine, and isodesmosine

• Hydroxyproline and hydroxylysine

• Gamma-carboxyglutamate

• Phosphoserine, phosphothreonine, and phosphotyrosine

• N-acetyl lysine

• Methyllysine

Non-Standard Amino Acids and Their Functions

Non-standard amino acids being an essential molecule in biochemistry, have some key functions that help humans to produce different things which act as useful products in their daily lives.

Some of the important functions of non-standard amino acids are as follow:

• The most important posttranslational modification of amino acids occurring in eukaryotic organisms is considered to be the reversible addition of a phosphate molecule to the hydroxyl portion of the R groups of serine, threonine, and tyrosine. The event is referred to as phosphorylation and gets used for regulating the activity of proteins that seem to be functioning in cells continuously. This is considered to be an important function of non-standard amino acids.

• Non-standard amino acids that are produced in industries are considered to have some important functions that can be very useful. The first commercial production of amino acids was in the year 1908. At that time, a flavouring agent, monosodium glutamate, was prepared using a type of large seaweed. Glycine and cysteine can also do the work as food additives, and some mixtures of amino acids are also used as flavour enhancers in some food industries. This is considered to be another important function of amino acids that is useful to humans.

List of Non-Standard Amino Acids

Non-standard amino acids which one cannot find in proteins are lanthionine, 2-aminoisobutyric acid, dehydroalanine, and the neurotransmitter gamma-aminobutyric acid. Non-standard amino acids are considered to be intermediaries that are present in the metabolic pathway of standard amino acids. In order to have a clear understanding, let’s discuss an example: ornithine and citrulline seem to occur in the urea cycle, which is considered to be a part of amino acid catabolism. Some other examples of non-standard amino acids are as follows:

• Cystine, desmosine, and isodesmosine: This type of amino acid is known to be found in extracellular matrix proteins such as elastin.

• Hydroxyproline and hydroxylysine: This type of amino acid is known to be found in one type of extracellular matrix, which is known as collagen.

• Gamma-carboxyglutamate: These are found in osteocalcin, which is considered to be a type of extracellular matrix that is found in bones but also in the prothrombin. This is considered to be important for the coagulation cascade.

• Phosphoserine, phosphothreonine, and phosphotyrosine: These are found in many different proteins. They’re known to be phospholipids and also to be found in intracellular membranes.

• Inositol: This type of amino acid is found in many kinds of viruses.