Biotech Articles
Publish Your Research Online
Get Recognition - International Audience

Request for an Author Account   |   Login   |   Submit Article
 
 
HOME FAQ TOP AUTHORS FORUMS PUBLISH ARTICLE
 
 

Synthesis and Significance of Non-Protein Amino Acids

BY: Divya Narayan | Category: Others | Submitted: 2016-05-30 04:35:53
       No Photo
Article Summary: "Non-Protein Amino (NPAAs) are those amino acids which are not coded for by DNA (not present in genetic code). These amino acids possess great significance in health, nutrition, and overall metabolism.."


Share with Facebook Share with Linkedin Share with Twitter Share with Pinterest Email this article
     


SYNTHESIS AND SIGNIFICANCE OF NON-PROTEIN AMINO ACIDS

What are non-protein amino acids?

Amino acids are the building blocks of proteins or peptides comprising of carbon, hydrogen, oxygen, sulphur, nitrogen, carboxylic acid, and amino groups.

However, there are certain amino acids which are not involved in primary metabolism, and are not part of any proteinic molecule. They are known as non-protein amino acids (NPAAs).

These amino acids are not coded for by the genetic code of the DNA. 1

NPAAs can occur in nature owing to the following conditions – 2

1. Metabolic intermediates

2. Post-translational modifications

3. Components of biomolecules

4. Pharmacologic agents

5. Experimental models

Classification

Non-protein amino acids can be classified on the basis of – 3

  • Functional Group
· Structural analogs of protein amino acids

  • Physiologic effects (Neurotoxic)
  • Miscellaneous


Synthesis

The synthesis of a few significant NPAAs are given below –

1. Citrulline – Citrulline is one of the most important non-proteinic amino acids. It was first isolated from watermelon (“Citrullus” in Latin) after which it is named. It is naturally present in the L-alpha form. The main source of Citrulline is watermelon. 4

In the body, Citrulline is one of the metabolic intermediates of the urea cycle. Arginine is converted to Nitric oxide with the help of the enzyme Nitric Oxide synthetase, liberating Citrulline as a by-product. 5

BA_3551_1

Additionally, amino acids such as Glutamate, Proline, etc., act as precursors of Citrulline. Intestinal epithelium converts Glutamate to Citrulline via the enzyme glutamate-5-semialdehyde, releasing carbamoyl phosphate as an intermediate. 6

In plants, citrulline is a by-product of the arginine biosynthetic pathway. It is synthesized in the chloroplast using ornithine as a precursor, and the reaction is catalyzed by the enzyme Ornithine transcarbamylase (OTC). 7

BA_3551_2

2. Ornithine - Ornithine is another NPAA produced as a metabolic by-product of the urea cycle. The body can produced ornithine on its own. Hence a deficiency of this amino acid is rare. The main sources of L-ornithine are chocolate, coconut, gelatin, meats, oats, soybeans, wheat germ, etc. 8

In the urea cycle, ornithine is synthesized from arginine with the help of the enzyme Arginase 1. Urea is released as a by-product which further continues the cycle. Hence ornithine can be regarded as the central molecule of the urea cycle. 9

BA_3551_3

In plants, ornithine is synthesized in the mitochondrion after arginine gets transported from the cytosol into the mitochondrion. This reaction is catalyzed by the enzyme Arginase. 10

BA_3551_4

3. Theanine - This amino acid is also known as N5-ethyl-L-glutamine. It is found in plants and fungi. This amino acid is known as 'theanine' as it was first discovered in green tea. The main sources of theanine are green tea, black tea, Japonica, etc. 11

In plants, biosynthesis of theanine takes place using L-glutamic acid as a precursor with glutaminase as the enzyme catalyzing the reaction. Ethylamine releases ammonia as a result of the reaction. 12

BA_3551_5


4. Trimethyglycine - Amino acid derivative first isolated from sugar beets. It is a trimethylated amino acid (glycine) which exists in the zwitterionic form at neutral pH. The main sources of trimethyglycine are beets, spinach, broccoli, shellfish, and whole grains. 13

In the body, synthesis of trimethylglycine takes place by oxidation reaction of choline and associated compounds. Choline upon oxidation produces betaine aldehyde with the help of the enzyme mitochondrial choline oxidase (choline dehydrogenase) in animals, choline monooxygenase in plants, and choline oxidase in bacteria. Further oxidation in the mitochondria results in the formation of trimethylglycine. This reaction is catalyzed by an NAD+ - dependent betaine aldehyde dehydrogenase enzyme. 14

BA_3551_6

5. Taurine - Taurine is a by-product of methionine and cysteine. But, taurine does not contain a carboxylic acid group. Therefore, it is an amino sulphonic acid. Taurine was first isolated from ox bile ("taurus") hence the name. The main sources of taurine are animal and fish protein, animal meat, eggs, brewer's yeast, etc. 16

In mammals, biosynthesis of taurine takes place via the cysteine sulfinic acid pathway. The enzyme cysteine dioxygenase oxidizes thiol group of cysteine to form sulfinic acid. Sulfinic acid undergoes decarboxylation with the help of sulfoalanine decarboxylase to form hypotaurine. Hypotaurine further undergoes enzymatic dehydrogenation (hypotaurine dehydrogenase) to form Taurine. 17

BA_3551_7

Significance

The significance of the above-mentioned NPAAs is as follows -

1. Citrulline - Citrulline is one of the amino acids recommended for therapeutics against erectile dysfunction. 19

Enzymes such as peptidylarginine deiminases convert arginine to citrulline. This citrulline is added on to some proteins during post-translational modification. Some of the proteins include myelin basic protein, filaggrin, histone proteins, etc. 20

Detection of antibodies bound to citrulline can be regarded as a biomarker for the detection of rheumatoid arthritis. 20

Citrulline has been found to protect muscle function during conditions of dietary restriction. 20

2. Ornithine - Ornithine is the precursor molecule of the amino acids citrulline, glutamic acid, and proline. 21

Ornithine also acts as a detoxification agent in the liver, reducing liver cirrhosis as well as other liver disorders. 21

Ornithine has also been to observe to reduce ammonia concentrations in the bloodstream. 21

3. Theanine - Dietary supplements containing theanine have been found to act as a relaxant and aid in stress reduction by altering levels of various neurotransmitters in the brain. Theanine possesses the ability to cross the blood brain barrier. 22

Theanine has also found to support the immune system by increasing the production of T lymphocytes. 23

4. Trimethyglycine - It can donate three methyl groups, which can be extremely useful in biochemical reactions. 24

Trimethylglycine works alongwith B-complex vitamins - Vitamin B6, Folic acid, Vitamin B12 - so as to assist in the formation of SAM (s-adenosyl methionine), an amino acid required for the brain. SAM also functions as an antidepressant in the brain. 25

Trimethylglycine also plays a role in the synthesis of carnitine which protects against kidney disorders. 26

Trimethylglycine has been used as therapy against the following health conditions - 27

- Hepatitis and Non-Alcoholic Steatohepatitis

- High Homocysteine

- Atherosclerosis

5. Taurine - Taurine helps lower cortisol levels as it controls anxiety and stress levels. It improves reaction time in athletes, thereby improving athletic performance. 28

Taurine also prevents diabetes by controlling insulin levels, as well as helps fight inflammation. Taurine also possesses the property of lowering lipid levels from the blood stream, which protects against cardiovascular disorders and helps reduce cholesterol. 28

Taurine also helps protect the liver against oxygen free-radicals. 29

In felines, taurine is required for proper development of retina. Hence feline meals should either contain fish protein (rich in taurine) or artificially enriched with taurine (cat food). Taurine deficiency in felines leads to degeneration of retina resulting in blindness, as well as loss of fur. 30

References

1. Non-proteinogenic amino acid. Available from http://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:83820 (Accessed on May 27, 2016)

2. Non-proteinogenic amino acids – Wikipedia, The Free encyclopedia. Available from https://en.wikipedia.org/wiki/Non-proteinogenic_amino_acids (Accessed on May 27, 2016)

3. D’Mello JPF. Toxicity of non-protein amino acids from plants. Available from https://www.google.co.in/search?tbm=bks&hl=en&q=Amino+Acids+and+Their+Derivatives+in+Higher+Plants (Accessed on May 27, 2016)

4. Citrulline – Wikipedia, The Free Encyclopedia. Available from https://en.wikipedia.org/wiki/Citrulline (Accessed on May 27, 2016)

5. CasePerformance: Nitric Oxide. Available from http://www.caseperformance.com/126/nitric-oxide-supp-s-part-i-understanding-the-key-players (Accessed on May 27, 2016)

6. PathwayCommons::Citrulline Biosynthesis. Available from http://www.pathwaycommons.org/pc/record2.do?id=505647 (Accessed on May 27, 2016)

7. Winter G, Todd CD, Trovato M, Forlani G and Funck D. Physiological implications of arginine metabolism in plants. Front. Plant Sci. 2015;6:534. doi: 10.3389/fpls.2015.00534

8. Bliss Returned. Ornithine: The amino acid that helps to prompt the release of growth hormone, which promotes the metabolism of excess body fat. Available from https://blissreturned.wordpress.com/2012/03/26/ornithine-the-amino-acid-that-helps-to-prompt-the-release-of-growth-hormone-which-promotes-the-metabolism-of-excess-body-fat/ (Accessed on May 27, 2016)

9. The Ornithine Cycle. Available from http://www.nature.com/nrm/journal/v1/n3/fig_tab/nrm1200_225a_F2.html (Accessed on May 27, 2016)

10. Funck D, Stadelhofer B, Koch W. Ornithine-δ-aminotransferase is essential for Arginine Catabolism but not for Proline Biosynthesis. BMC Plant Biology. 2008;8:40. doi:10.1186/1471-2229-8-40

11. Theanine. Available from https://examine.com/supplements/theanine/ (Accessed on May 27, 2016)

12. L-Theanine synthesis. Available from http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/Articleimage/2014/RA/c3ra45315d/c3ra45315d-s1_hi-res.gif (Accessed on May 27, 2016)

13. Trimethylglycine. Available from https://examine.com/supplements/trimethylglycine/ (Accessed on May 27, 2016)

14. Choline and Betaine Uptake and Betaine Biosynthesis. Available from http://www.phantome.org/PhageSeed/SubsysEditor.cgi?page=ShowSubsystem&subsystem=Choline_and_Betaine_Uptake_and_Betaine_Biosynthesis (Accessed on May 27, 2016)

15. Alpha-GPC gave man (79) uncontrollable libido. Available from http://www.ergo-log.com/alpha-gpc-gave-man-79-uncontrollable-libido.html (Accessed on May 27, 2016)

16. What is Taurine Derived From? Available from http://www.whathealth.com/taurine/overview.html (Accessed on May 27, 2016)

17. Taurine – Wikipedia, The Free encyclopedia. Available from https://en.wikipedia.org/wiki/Taurine#Biosynthesis (Accessed on May 27, 2016)

18. Menzie J, Prentice H, Wu J-Y. Neuroprotective Mechanisms of Taurine against Ischemic Stroke. Brain Sciences. 2013;3(2):877-907. doi:10.3390/brainsci3020877

19. Erectile Dysfunction and L-Citrulline. Available from http://www.healthline.com/health/erectile-dysfunction/l-citrulline (Accessed on May 27, 2016)

20. Citrulline – Wikipedia, The Free Encyclopedia. Available from https://en.wikipedia.org/wiki/Citrulline#Function (Accessed on May 28, 2016)

21. The Amino Acid Ornithine. Available from http://www.vitaminstuff.com/amino-acid-ornithine.html (Accessed on May 28, 2016)

22. L-Theanine - Sex Drive Support / Dopamine / Glutamate. Available from http://www.smartbodyz.com/L-Theanine-Information.htm (Accessed on May 28, 2016)

23. Bukowski JF, Percival SS. L-theanine intervention enhances human γδ T lymphocyte function. Nutrition Reviews. 2008;66(2):96-102. doi: 10.1111/j.1753-4887.2007.00013.x

24. Trimethylglycine or TMG. Available from http://drlwilson.com/Articles/TRIMTHYLGLYCINE.htm (Accessed on May 28, 2016)

25. TMG (Trimethylglycine). Available from https://www.solal.co.za/tmg (Accessed on May 28, 2016)

26. Trimethyglycine (TMG, Betaine) Powder. Available from http://www.nutrabio.com/Products/trimethylglycine.htm (Accessed on May 28, 2016)

27. Betaine (Trimethylglycine). Available from http://www.mottchildren.org/health-library/hn-2807004 (Accessed on May 28, 2016)

28. Ten Benefits of Taurine. Available from http://main.poliquingroup.com/ArticlesMultimedia/Articles/Article/782/Ten_Benefits_of_Taurine.aspx (Accessed on May 28, 2016)

29. ZHANG Z, LIU D, YI B, et al. Taurine supplementation reduces oxidative stress and protects the liver in an iron-overload murine model. Molecular Medicine Reports. 2014;10(5):2255-2262. doi:10.3892/mmr.2014.2544

30. Taurine – Wikipedia, The Free Encyclopedia. Available from https://en.wikipedia.org/wiki/Taurine#In_animal_nutrition (Accessed on May 28, 2016)



About Author / Additional Info:
I am a post-graduate in Biochemistry from the University of Mumbai

Search this site & forums
Share this article with friends:



Share with Facebook Share with Linkedin Share with Twitter Share with Pinterest Email this article

More Social Bookmarks (Digg etc..)


Comments on this article: (0 comments so far)

Comment By Comment

Leave a Comment   |   Article Views: 2688



Additional Articles:

•   Plastid Terminal Oxidase (PTOX) - Its physiological role and biological significance

•   The Therapeutics of Biopharmaceutical Substances

•   Edible Vaccines - Immunization with Plants or Food

•   Biocontrol Potential of Compost




Latest Articles in "Others" category:
•   Biotechnology, Its Techniques and Human Health

•   Techniques of Biotechnology

•   Nanomedicine and Disease Treatment

•   Biotechnology and Livestock

•   Bioinformatics: Combination of Biotechnology and Information Technology

•   Gene Patenting and Its Uses

•   Polymerase Chain Reaction: A Technique of Biotechnology

•   Pharmacogenomics: Benefits and Barriers

•   Human Genome Project: Ethical and Legal Issues

•   Plant and Animal Tissue Culture: Procedure, Benefits and Limitations

•   Therapeutics and Biotechnology

•   Biotechnology: A Revolutionary Field and Biotech Challenges

•   Recombinant DNA Technology

•   Environment and Biotechnology

•   Biosensors: Role in Biotechnology

•   Human Insulin and Recombinant DNA Technology

•   Biotechnology and Its Applications

•   Genetic Engineering and its Methods

•   Types of Gene Mutations - Diseases Caused By Gene Mutation



Important Disclaimer: All articles on this website are for general information only and is not a professional or experts advice. We do not own any responsibility for correctness or authenticity of the information presented in this article, or any loss or injury resulting from it. We do not endorse these articles, we are neither affiliated with the authors of these articles nor responsible for their content. Please see our disclaimer section for complete terms.
Page copy protected against web site content infringement by Copyscape
Copyright © 2010 biotecharticles.com - Do not copy articles from this website.

ARTICLE CATEGORIES :
Agriculture Bioinformatics Applications Biotech Products Biotech Research
Biology Careers College/Edu DNA Environmental Biotech
Genetics Healthcare Industry News Issues Nanotechnology
Others Stem Cells Press Release Toxicology  


  |   Disclaimer/Privacy/TOS   |   Submission Guidelines   |   Contact Us