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

Proteinogenic and non-proteinogenic amino acids are two distinct categories of amino acids based on their involvement in protein synthesis and their natural occurrence in organisms. Here are the key differences between the two:

1. Incorporation into proteins: Proteinogenic amino acids are incorporated into proteins through translation, while non-proteinogenic amino acids are not naturally incorporated into proteins.
2. Number of amino acids: There are 22 genetically encoded (proteinogenic) amino acids, 20 in the standard genetic code and an additional 2 (selenocysteine and pyrrolysine) that can be incorporated by special translation mechanisms. In contrast, there are over 140 non-proteinogenic amino acids that occur naturally in proteins, and thousands more may occur in various biological and chemical contexts.
3. Essentiality: Humans can synthesize 12 of the 21 proteinogenic amino acids from each other or from other molecules of intermediary metabolism. The other nine must be consumed (usually as their protein derivatives) and are called essential amino acids. Non-proteinogenic amino acids are not essential for protein synthesis.
4. Functions: Many non-proteinogenic amino acids have important roles in biosynthesis, post-translational formation of proteins, physiological roles (e.g., components of bacterial cell walls, neurotransmitters, and toxins), as natural or man-made pharmacological compounds, or in prebiotic experiments.

In summary, proteinogenic amino acids are involved in the generation of proteins and are essential for various biological functions, whereas non-proteinogenic amino acids are not incorporated into proteins and have diverse roles in various biological and chemical contexts, including post-translational protein modifications and serving as neurotransmitters or toxins.

Comparative Table: Proteinogenic vs Non-proteinogenic Amino Acids

Here is a table comparing proteinogenic and non-proteinogenic amino acids:

In summary, proteinogenic amino acids are incorporated into proteins during translation and are encoded in the genetic code of organisms, while non-proteinogenic amino acids are not incorporated into proteins and are not encoded in the genetic code. Proteinogenic amino acids have various functions like enzymes and hormones, while non-proteinogenic amino acids serve as intermediates in biosynthesis and have other physiological roles.