Amino Acid Metabolism

Amino acid metabolism is an important process that occurs within the human body to assist in numerous biological reactions. This article will cover the role of glutamate, transamination reactions, and various types of amino acids such as glycogenic, ketogenic, and mixed amino acids.

Glutamate and Transamination Reactions

The four most common amino acids in the human body are glutamate, aspartate, alanine, and glutamine and each has major metabolic functions and roles in the body.

Glutamate has a similar chemical structure to 2-oxoglutarate, which is an intermediate substance in the Krebs cycle of the body. Glutamate and 2-oxoglutarate exist in equilibrium and can be converted by transaminases or glutamate dehydrogenase. Glutamate can also be converted to glutamine, which is the most common free amino acid in human blood plasma and can be a carrier of nitrogen in the body.

Glutamate is the most prevalent and has important roles to play in bodily functions. Of note when it comes to metabolism, glutamate has a central part in the breakdown of amino acids. For example, the glutamate pool is essential for excreting nitrogen from dietary protein from the body.

Transamination is a reaction that involves the conversion of an amino acid to the corresponding keto acid. In this type of reaction, the amino group from an amino acid swaps to another keto acid so that there is a new pairing of amino acid and keto acid. There is no net loss or gain of nitrogen in this type of reaction. Transamination reactions are reversible with an equilibrium constant that is close to 1.

Introduction to Amino Acid Metabolism

Glycogenic, Ketogenic, and Mixed Amino Acids

The majority of amino acid carbon skeletons are degraded to intermediates of the Krebs cycle after transamination. As a result, they can increase the blood glucose levels via the gluconeogenic pathway.

These amino acids were traditionally known as “glycogenic” amino acids because it was observed that they had a tendency to worsen diabetic glycosuria for this reason:

  • Alanine: made from and degraded to pyruvate
  • Arginine: made from and degraded to glutamate
  • Asparagine: made from and degraded to aspartate
  • Aspartate: made from and degraded to oxaloacetate
  • Cysteine: an essential amino acid that can be made from methionine and degraded to pyruvate
  • Glutamate: made from and degraded to oxoglutarate
  • Glutamine: made from and degraded to glutamate
  • Glycine: made from serine with multiple pathways of degradation
  • Histidine: an essential amino acid that can be degraded to glutamate
  • Methionine: an essential amino acid that can be degraded to propionyl-CoA
  • Proline: made from and degraded to glutamate
  • Serine: made from phosphoglycerate and degraded to pyruvate
  • Threonine: an essential amino acid with unknown degradation products
  • Valine: an essential amino acid that can be degraded to propionyl-CoA

“Ketogenic” amino acids tend to worsen diabetic ketoacidosis and are typically degraded to acetoacetate or acetyl-CoA. Leucine is an example of this type, which is an essential amino acid that can be degraded to acetyl-CoA.

“Mixed” amino acids can be degraded both to amino acids of the Krebs cycle and to acetyl-CoA, with characteristics of both glycogenic and ketogenic amino acids.

  • Isoleucine: an essential amino acid that can be degraded to acetyl-CoA and propionyl-CoA
  • Lysine: an essential amino acid with unknown degradation products
  • Phenylalanine: an essential amino acid that can be degraded to tyrosine
  • Tryptophan: an essential amino acid with unknown degradation products
  • Tyrosine: an essential amino acid that can be made from phenylalanine and degraded to fumarate and acetoacetate.

References

Last Updated: Feb 26, 2019

Yolanda Smith

Written by

Yolanda Smith

Yolanda graduated with a Bachelor of Pharmacy at the University of South Australia and has experience working in both Australia and Italy. She is passionate about how medicine, diet and lifestyle affect our health and enjoys helping people understand this. In her spare time she loves to explore the world and learn about new cultures and languages.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Smith, Yolanda. (2019, February 26). Amino Acid Metabolism. News-Medical. Retrieved on October 10, 2024 from https://www.news-medical.net/life-sciences/Amino-Acid-Metabolism.aspx.

  • MLA

    Smith, Yolanda. "Amino Acid Metabolism". News-Medical. 10 October 2024. <https://www.news-medical.net/life-sciences/Amino-Acid-Metabolism.aspx>.

  • Chicago

    Smith, Yolanda. "Amino Acid Metabolism". News-Medical. https://www.news-medical.net/life-sciences/Amino-Acid-Metabolism.aspx. (accessed October 10, 2024).

  • Harvard

    Smith, Yolanda. 2019. Amino Acid Metabolism. News-Medical, viewed 10 October 2024, https://www.news-medical.net/life-sciences/Amino-Acid-Metabolism.aspx.

Comments

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment
Post

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.

You might also like...
Human gut microbiome: A source of new antibiotic peptides