Types of amino acid

So far, about 80 types of amino acids have been identified. Among these, 20 are thought to be in human body. Plants synthesize amino acid through photosynthesis. Animals, on the other hand, obtain protein through ingesting plants or other animals. Ironically, plants that can synthesize amino acids cannot utilize nitrogen molecules in the air. They absorb from the soil bacterial synthesizedamino group, nitrate group, and nitrite group, etc. to synthesize amino acids.

Natural amino acids form a mirror structure of L shaped and D shaped isomers. All amino acids have isomers except for glycerine whose structure is very simple. All amino acids that form organisms are L-form. Carbohydrate components consumed by organisms are all D-form. For example, glucose is a D-form (D-glucose) and is also called dextrose.

 

Categorization based on side chain polarity

Amino acidcan be categorized in different ways based on the chemical structure or function. Let us first look at categorization based on the chemical structure, especially the side chain. Amino acids can be divided into four types. I understand that not everyone is fond of looking at chemical formulae but it is not all that complicated. It is important to understand the structures of proteins and peptides (Image 3).

 

HELIOSⅡ/LOTUSⅡ/HYPERION – Manufacturer: LASEROPTEK(www.laseroptek.com)

 

1) Nonpolar, aliphatic or hydrophobic amino acid

There are nine nonpolarorhydrophobicamino acids: glycine, ,alanine, valine, leucine, isoleucine, phenylalanine, tryptophan, and proline. They have side chains that consist only of hydrogen and carbon. For example, glycine, the simplest form of amino acid has two hydrogen atoms attached to an α-carbon. The second simplest amino acid is alanine which has a methyl group (-CH3) side chain. Amino acids with a more complicated hydrocarbon side chain are valine, leucine, and isoleucine. They have a branched shape and are called BCAA.

Methionine contains the thiol group(-S-). Among amino acids with an aromatic side chain, phenylalanine andtryptophan are hydrophobic amino acids. Prolinehas a hydrocarbonside chain that bonds to a nitrogen atom and forms a unique hook shape. Strictly speaking, proline has an imine group and can be categorized as an imino acid but as it acts together with the other 19 amino acids, it is regarded as an amino acid.

These nine hydrophobicamino acids gather together to form protein to avoid the hydrophilic cellular environment. This is how proteins form a tight structure.

 

-To be continued-