What is the Difference Between Proteinogenic and Non-Proteinogenic Amino Acids

The main difference between proteinogenic and non-proteinogenic amino acids is that proteinogenic amino acids are naturally encoded by the genome for the assembly of proteins, whereas non-proteinogenic amino acids are not encoded by the genome for the assembly of proteins.

Proteinogenic and non-proteinogenic amino acids are two types of amino acids that occur in proteins as well as in nature. They contain both amino groups and carboxyl groups as functional groups.  

Key Areas Covered

1. What are Proteinogenic Amino Acids
     – Definition, Structure, Function
2. What are Non-Proteinogenic Amino Acids
     – Definition, Structure, Function
3. Similarities Between Proteinogenic and Non-Proteinogenic Amino Acids
     – Outline of Common Features
4. Difference Between Proteinogenic and Non-Proteinogenic Amino Acids
     – Comparison of Key Differences

Key Terms

Non-Proteinogenic Amino Acids, Proteinogenic Amino Acids

What is Proteinogenic Amino Acids

Proteinogenic amino acids are the amino acids that are incorporated into proteins during translation. They are encoded by the genetic code of organisms. There are 22 proteinogenic amino acids. Among them, 20 amino acids are encoded by the genetic code of organisms, while the other two, selenocysteine and pyrrolysine, are incorporated into the proteins using special mechanisms of translation. In eukaryotes, there are 21 proteinogenic amino acids: 20 amino acids encoded by the genetic code plus selenocysteine. Furthermore, there are two types of proteinogenic amino acids: essential amino acids and non-essential amino acids. Essential amino acids are not synthesized during metabolism. Therefore, they need to be added to the diet. Some of the essential amino acids include histidine, leucine, isoleucine, lysine, methionine, threonine, tryptophan, phenylalanine, and valine.

Figure 1: Proteinogenic Amino Acids

Moreover, non-essential amino acids are the amino acids that are produced inside the human body during metabolism. Alanine, asparagine, cysteine, aspartic acid, glutamine, glutamic acid, glycine, proline, serine, and tyrosine are examples of non-essential amino acids.

What are Non-Proteinogenic Amino Acids

Non-proteinogenic amino acids are distinct amino acids from the 22 proteogenic amino acids. Therefore, they do not incorporate into proteins during translation.  The genetic code of the organisms does not encode these amino acids. However, there are more than 140 non-proteinogenic amino acids. These non-proteinogenic amino acids either occur in nature or are synthesized inside the laboratory. Examples of non-proteinogenic amino acids include ornithine, citrulline, and gamma-aminobutyric acid (GABA).

Figure 2: Non -Proteogenic Amino Acids

Moreover, non-proteinogenic amino acids have different functions, such as being intermediates in biosynthesis, participating in the post-translational formation of proteins, and other physiological roles, like being components of bacterial cell walls, neurotransmitters, and toxins, presence in pharmacological compounds, etc.

Similarities Between Proteinogenic and Non-Proteinogenic Amino Acids

• Proteinogenic and non-proteinogenic amino acids are two types of amino acids occurring in proteins.
• They play a significant role in the metabolism.

Difference Between Proteinogenic and Non-Proteinogenic Amino Acids

Definition

Proteinogenic amino acids refer to amino acids that are incorporated biosynthetically into proteins during translation, while non-proteinogenic amino acids refer to amino acids other than the 20 amino acids incorporated in protein.

Genetic Code

Proteinogenic amino acids are encoded in the genetic code of organisms, while non-proteinogenic amino acids are not encoded by the genetic code of organisms.

In Translation

While proteinogenic amino acids are incorporated into proteins during translation, non-proteinogenic amino acids are not incorporated into the proteins during translation.

Function

Proteinogenic amino acids undergo functions like enzymes, hormones, and structural proteins, while non-proteinogenic amino acids serve as intermediates in biosynthesis and involve in different physiological roles.

Examples

Proteinogenic amino acids include glycine, alanine, and valine, while non-proteinogenic amino acids include ornithine, citrulline, and gamma-aminobutyric acid.

Conclusion

In brief, proteinogenic and non-proteinogenic amino acids are two types of amino acids that occur in nature and proteins. Proteinogenic amino acids are incorporated into proteins during translation. They are encoded by the genetic code of the organism. Their function is to serve as structural proteins, enzymes, and hormones. Glycine, alanine, and valine are examples of proteinogenic amino acids. In comparison, non-proteinogenic amino acids are amino acids that do not incorporate into proteins during translation. Therefore, they are not encoded by the genetic code of the organism. Ornithine, citrulline, and gamma-aminobutyric acid are examples of non-proteogenic amino acids. Overall, the main difference between proteinogenic and non-proteinogenic amino acids is their incorporation into proteins during translation.

References:

1. “Proteinogenic amino acid.” Wikipedia. Wikimedia Foundation. 
2. “Non-proteinogenic amino acids.” Wikipedia. Wikimedia Foundation. 

Image Courtesy:

1. “Proteinogenic Amino Acid Table” By Thomas.ryckmans68 – Own work (CC-BY SA 4.0) via Commons Wikimedia
2. “Nonproteinogenic AAs.” By Matteo Ferla – Own Work (CC-BY SA 4.0) via Commons Wikimedia