Proteinogenic amino acidsThere are many different types of amino acids in nature. However, the chemical structure, which unites them all is a carboxy (-COOH) group and at least one amino group (-NH2).

Although scientists are still learning about these important organic compounds, our understanding of their benefits to humans is fairly good.

Proteinogenic amino acids

One group of amino acids that are very important to humans are classified as proteinogenic amino acids. They represent a very small fraction of all the known amino acids. However they are vital because they help to build proteins within the body.

Proteinogenic amino acids are incorporated into proteins during a process called translation. There are twenty biologically active proteinogenic amino acids. These are further classified into ‘essential’, ‘non-essential’ and ‘semi-essential’.

Different groups of proteinogenic amino acids

Essential amino acids cannot be synthesised by the body. These compounds need to be obtained from dietary sources. Non-essential amino acids are those compounds which our body can easily produce.

However, there can be times where non-essential amino acids become semi-essential. For example, if you become ill there will be an increased need for certain compounds to sustain the immune system defence mechanism. This can lead to deficiencies in certain nutrients.

If your diet is compromised, it’s possible that you will also be struggling to produce non-essential amino acids. These are some of the situations where a non-essential amino acid can become a semi-essential amino acid.

While proteinogenic amino acids are critical for the development of various proteins, they also perform many other roles within the human body.

Essential proteinogenic amino acids

There are nine essential proteinogenic amino acids that the body must source from diet. These include:


This proteinogenic amino acid is considered essential, although this is usually only during childhood. Once an adult, they body is able to synthesise enough of this amino acid.



This essential amino acid is one of three branched chain amino acids, together with valine and leucine.


This essential amino acid is one of three branched chain amino acids, together with isoleucine and valine.


In addition to helping to build proteins, this amino acid has been used with varying success to treat herpes infections.


Together with cysteine, this is one of two proteinogenic amino acids that contain sulphur.



This proteinogenic amino acid occurs naturally in the breast milk of mammals. It is converted into another amino acid, L-tyrosine.


This proteinogenic amino acid is sometimes used in treatments for nervous system disorders.


In addition to building protein, this essential amino acid is also a biochemical precursor to a range of other compounds including serotonin, niacin, and auxin.


This essential amino acid is one of three branched chain amino acids, together with isoleucine and leucine.

Non-essential proteinogenic amino acids

There are eleven non-essential proteinogenic amino acids. However, it’s important to remember that they can become semi-essential in times of stress.


This amino acid plays many roles in the body and is particularly important for the synthesis of nitric oxide. In some cases this proteinogenic amino acid is semi-essential and supplementation may be necessary.


One of the most commonly used amino acids in protein synthesis is L-alanine. This compound can also be found in a less common form known as D-alanine


The nervous system requires this amino acid to function properly. It is also involved in the production of ammonia, and amino acid transformation.

Aspartic acid

Closely related to asparagine, this amino acid is an important neurotransmitter.


One of only two sulphur containing proteinogenic amino acids, cysteine is involved in protein cross-linking.


In addition to protein synthesis, this amino acid is vital to nitrogen metabolism.

Glutamic acid

This amino acid plays a key role in cellular metabolism.  It is a very important neurotransmitter.


A central nervous system inhibitory neurotransmitter, this amino acid also makes up a large portion of the structural protein collagen.


In addition to building proteins, this amino acid is also used as asymmetric catalysts in organic reactions


This proteinogenic amino acid is important in metabolism and in catalytic functions of various enzymes.


In addition to building proteins, this amino acid is also important in the production of various hormones in the body.



Proteins are essential for our body to function and repair itself. To synthesis proteins, the body requires proteinogenic amino acids.  Some of these can be synthesised within the body, while others need to be sourced externally through diet. During periods of stress, some non-essential amino acids may become semi-essential.

It’s important to maintain a healthy balanced diet to ensure that the body has access to enough proteinogenic amino acids to function optimally. In some cases dietary supplements may be beneficial.