#8-3. Amino Acid IVNT Overview I

2) Polar, hydrophilic amino acid

Polar, hydrophilic amino acids are serine, threonine, cysteine, tyrosine, asparagine and glutamine.

Amino acids that have neutral molecules but also a hydroxyl group (-OH) that contains an oxygen atom with strong electronegativity include serine, threonine, and tyrosine. Tyrosine is an aromatic amino acid and has a similar structure to that of phenylalanine. Amino acids that have hydrophilic -OH in their chemical structure are categorized as hydrophilic amino acid.

Cysteine is similar to serine but has -SH group called thiol or sulfhydryl. -SH is more reactive than -OH and can form thiol ion (-S-) with mild base. Two -SH bond to form -S-S- (disulfide bond). Asparagine and glutamine that have carboxamide are also polar amino acids.

3) Acidic amino acids

Aspartic acid and glutamic acid are acidic amino acids and they both have a carboxyl group side chain. At neautral pH levels, the two amino acids lose hydrogen from the carboxyl gorup side chain and exist in negative ion. To indicate the negative electric charge, they are also called aspartate and glutamate.

4) Basic amino acids

Lysine, arginine and histidine belong in this group. They each have amine group, guanidium group, and imidazole group. They are basic amino acids that have positive electric charge at neutral pH and exist mainly at enzyme active sites.

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Essential and non-essential amino acids

Protein is degraded into amino acids in the body and are absorbed and utilized in various ways. The nutrition of a protein is determined by the type of amino acids comprise it. There are amino acids that are biologically synthesized and those that need to be ingested. non-essential amino acids are biosynthesized in the body using metabolic intermediates of sacchrides, nitrogen, or they can be biosynthesized using essential amino acids. On the other hand, essential amino acids are biosynthesized in very small amounts or not at all and need to be supplemented through food.

Essential amino acids for adults are valine, leucine, isoleucine, methionine, threonine, lysine, phenylalanine, and tryptophan. Those for children include the eight above and histidine. Recently, arginine has been added to the list of essential amino acids for children.

Histidine and arginine are considered essential amino acids in children because they are no biosynthesized sufficiently to help release the growth hormones. In adults, histidine and arginine can be biosynthesized through the urea cycle.

Branched chain amino acid (BCAA)

BCAAs refer to these three amino acids; valine, leucine, and isoleucine. BCAAs are involved in muscle synthesis and make up over a third of essential amino acids that comprise muscle proteins. They also help to form a close aggregation of muscle cells to prevent muscle loss. Therefore, BCAAs are very important amino acids for athletes including body builders or marathoners.

Valine is involved in muscle regeneration, brain function and activity and emotional stability. Leucine participates in wound healing, blood sugar stabilization, muscle cell metabolism and hemoglobin generation. Along with leucine, isoleucine is also involved in muscle cell metabolism and hemoglobin generation.

BCAAs are important for muscle strength but they are important for liver health. Protein synthesis and metabolism occur in the liver and this can be a source of stress in case of liver dysfunction. BCAAs are not metablized in the liver but in the muscle and have no impact on the liver. BCAAs are also known to help activate hepatocyte growth factors to improve liver functions. A recent study found they helped prevent liver cirrhosis and liver cancer. The treatment goal for liver cirrhosis is not a cure but preserving the remaining liver function and inhibit progression into cancer.

Numbers such as 95% and 90% can be seen in amino acid solution packaging. Some patients confuse these numbers with the actual amino acid concentration level. If “BCAA/EAA” is written next to the number, it refers to the BCAA content among essential amino acids. If “BCAA/TAA” is written, the number refers to BCAA content among total amino acids (Image 2).