Methionine: Structure, Production & Benefits

Instructor: Brekke Peterson Munks
Have you ever heard of the amino acid methionine? In this lesson you will learn about the structure, production and benefits of methionine. After learning about methionine, you can check your understanding by taking a quiz.


Methionine is one of 20 amino acids that are needed for daily life in animals. This amino acid is not made in the bodies of animals and must be consumed in food, making it an essential amino acid. Methionine is made in plants and microorganisms. Do you ever crave foods rich in protein? If the answer is yes, you might need the amino acid methionine because this amino acid is vital in making proteins in the body.

The Structure of Methionine

Methionine is one of two amino acids that contain the element sulfur; the other is cysteine. The chemical formula of methionine is C5H11NO2S. In general, all amino acids have the same structure: an amino group attached to a hydrogen, a carboxyl group and a side chain group, denoted by 'R' via a central carbon. The amino and carboxyl groups and central carbon are considered the amino acid backbone, which is the same in all amino acids. It is the side chain that is specific to each different amino acid.

Amino acid structure
Amino acid structure

The side chain of methionine is C2H7S. Methionine is a linear molecule, meaning that its side chain doesn't branch into a 'y' shape, but instead each molecule is lined up in a straight line. Methionine is also denoted by Met or M in literature.

Methionine structure.

Production of Methionine

Methionine, as previously mentioned, is not produced in animal bodies. Instead, it must be consumed via high protein sources such as meat, dairy, poultry, liver, beans and eggs. In plants and microbes, methionine can be made through a process called methionine biosynthesis. This process starts with a molecule called aspartic acid, which is another amino acid. This molecule is reduced into a molecule called homoserine, which is also vital in threonine production (another amino acid). Homoserine then becomes active using a phosphate molecule. The hydroxyl, or -OH active group, is then replaced by another amino acid like cysteine or a derivative of methionine. This allows the sulfur molecule to bind. Then the molecules goes through methylation, the addition of CH3.

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