What is the Difference Between Methionine and Selenomethionine

The key difference between methionine and selenomethionine is that methionine is an essential protein-making amino acid typically containing sulfur, whereas selenomethionine is a derivative of methionine containing selenium bound to the amino acid methionine.

Methionine is an essential amino acid for humans. Selenomethionine is a naturally occurring amino acid containing a selenium atom bound to a methionine amino acid.

CONTENTS

1. Overview and Key Difference
2. What is Methionine 
3. What is Selenomethionine
4. Methionine vs Selenomethionine in Tabular Form
5. Summary – Methionine vs Selenomethionine

What is Methionine?

Methionine is an essential amino acid for humans. It plays a critical role in metabolism and health; it is also a part of angiogenesis (growth of new blood vessels). Moreover, supplements of methionine can help people suffering from copper poisoning. The codon that encodes this amino acid is AUG. Methionine can exist in two forms as D isomer and L isomer or as a mixture of both.

DL methionine is a mixture of the two enantiomers D-methionine and L-methionine. Therefore, it contains a mixture of two types of the same compound. We call this “racemethionine” because a mixture of D and L enantiomers is called a racemic mixture. It appears as a white crystalline powder or as small flakes. It also dissolves in water sparingly and is very slightly soluble in ethanol.  DL methionine is used as a dietary supplement. It has lipotropic action. Moreover, it is sometimes given to dogs as it can help to reduce the chances of stones in dogs.

L methionine is the L enantiomer of the amino acid methionine. Often, L methionine is the compound we call commonly “methionine”. It was first discovered by the American scientist John Howard Mueller (1921). Further, it is an essential amino acid in our body that is important for the formation of proteins. We can find this amino acid in some food such as meat, fish, and dairy products.

Moreover, this amino acid is very important in the growth of new blood vessels. It is also essential for tissue repair. In addition, it is a sulfur-containing amino acid and is involved in many detoxifying processes in our body, i.e. protects cells from pollutants. Furthermore, it slows cell aging and is essential for the absorption of selenium and zinc.

What is Selenomethionine?

Selenomethionine is a naturally occurring amino acid containing a selenium atom bound to methionine amino acid. It is abbreviated as SeMet. The major form that occurs naturally is L-isomer of selenomethionine. It is the main form of selenium that we can find in Brazil nuts, cereal grains, soybeans, and grassland legumes, etc.

The chemical formula for this substance is C5H11NO2Se, and the molar mass is 196 g/mol. It is randomly incorporated in place of methionine and is readily oxidized. This substance has an antioxidant nature, which arises from its ability to deplete reactive oxygen species. Moreover, selenium and methionine play a separate role in the formation and recycling of glutathione.

What is the Difference Between Methionine and Selenomethionine?

Methionine is an essential amino acid for humans. Selenomethionine is a naturally occurring amino acid containing a selenium atom bound to a methionine amino acid. The key difference between methionine and selenomethionine is that methionine is an essential protein-making amino acid typically containing sulfur, whereas selenomethionine is the derivative of methionine containing selenium bound to the amino acid methionine.

The following infographic presents the difference between methionine and selenomethionine in tabular form for side by side comparison.

Summary – Methionine vs Selenomethionine

Methionine is an essential amino acid for humans. Selenomethionine is a naturally occurring amino acid containing a selenium atom bound to a methionine amino acid. The key difference between methionine and selenomethionine is that methionine is an essential protein-making amino acid typically containing sulfur, whereas selenomethionine is the derivative of methionine containing selenium bound to the amino acid methionine.

Reference:

1. “Methionine.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine.

Image Courtesy:

1. “Methionin – Methionine” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
1. “Selenomethionine-2D-skeletal” By Ben Mills – Own work (Public Domain) via Commons Wikimedia