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Amino Acids: Is There Anything They Don't Do?

All you need to know about the functions that amino acids contribute to in the body.
18th Sep 2017

Hi everyone, it’s Nicola here again! Blog two coming up to keep you posted on my progress. 

I’ve been learning lots about amino acids since my first blog. One thing I’ve found really interesting is the diversity of functions that amino acids contribute to in the body.

The diversity of amino acids structures enable remarkable functions in the body which include energy source, tissue repair and wound healing, immune function, central nervous system and neurotransmitters, enzyme formation and collagen production, ammonia detoxification and acid-base balance as well as muscle growth.
I knew when writing the first blog, that the proteins that make up our body carry out essential day to day processes that are required for life. I also knew that amino acids compose the different proteins that make up our body, but how vital amino acids are to our functioning is truly remarkable. 

There are 20 standard amino acids that compose proteins; these are described in my first blog. After my first blog was published, I received a few queries regarding two amino acids; pyrrolysine and selenocysteine. Looking in to them, I found that they are not considered standard amino acids as they don’t appear in genetic codes. However, they are incorporated into the proteins during the translation stage of protein production.  

Selenocysteine and pyrrolysine are encoded by genes that usually function as stop signals for coding sequences of nucleic acids. Pyrrolysine is used in the biosynthesis of proteins in bacteria, while selenocysteine is located in the active sites of enzymes that participate in oxidation–reduction reactions.

Each amino acid is composed of an amine (NH2), a carboxyl group (COOH). Side chains attached to the carboxyl group determine the polarity of an amino acid, meaning they determine their positive or negative charge, which in turn impacts their metabolic pathways and functionality.  

Amino acids are essential for normal bodily functions like energy production, growth and development, tissue repair and wound healing, immune system and central nervous system function to name a few. 

The different amino acids are associated with interesting and various functions in the body. Here is a summary of the associations I found so far
  • Energy Source
    Alanine, asparagine, leucine, isoleucine, glutamine and glycine support the production of energy that is used all over the body.  
  • Tissue Repair and Wound Healing
    Arginine, isoleucine, leucine, lysine and proline are required in tissue repair and wound healing of the body. 
  • Immune Function
    Arginine, glutamine, lysine, histidine, methionine, proline, threonine are all involved in maintaining and improving immune function. 
  • Central Nervous System and Neurotransmitters
    Aspartic acid, glutamic acid, glycine, phenylalanine, tryptophan and tyrosine are needed for the function of the CNS. Some of these amino acids act as neurotransmitters, which are chemicals essential for the communication of information from the CNS to the rest of the body.
  • Enzyme Formation and Collagen Production
    Cysteine, lysine serine and tyrosine are required for the production of collagen, and subsequent protein formation, and for the formation of enzymes. 
  • Ammonia Detoxification and Acid-Base Balance
    Arginine, asparagine and glutamine are all involved in maintaining acid-base balance in the body, either by detoxifying ammonia in the liver, or, in the case of glutamine, by removing the ammonia molecule from its structure, and excreting it from the body in the urine. 
  • Muscle Growth
    Glycine, valine and leucine are required in the stimulation of muscle growth, particularly leucine, which also prevents muscle breakdown, resulting in the growth of muscle. 
Knowing the amino acid pattern of foods is important for Nutritional Epidemiology and investigation into associations between amino acid intake and health and disease. However, publications on amino acid intake in the UK and Irish population are limited. This is due to a lack of reliable data relating to amino acid composition of commonly consumed foods. 

The most reliable way to determine the amino acid content of food is through three procedures; Protein Hydrolysis, Reversed-Phase High Performance Liquid Chromatography, and Isotope Dilution Chromatography, which are considered the gold standards for amino acid quantification. This is due to the speed at which they can be conducted, the sensitivity of the analysis and the reproducibility of the data compared to other techniques. There are food composition databases that include complete amino acid patterns of foods, which include US food composition tables, Australian food composition tables, New Zealand food composition tables and German food composition tables. These composition tables are generally updated every 3-5 years.  

I am starting to look at ways to use our existing data to estimate accurate amino acid values for the food composition data used in the UK and Ireland*. I look forward to keeping you posted with my progress. 

As always, get in touch if you have any questions or comments at [ATTN: Nicola]. 

See you all next time! 

*McCance & Widdowson. Composition of foods integrated dataset (CoFID) 2015 [Available from: