Proline

Proline is an amino acid that is used in the biosynthesis of protein. It is non-essential in humans, meaning the body can synthesize it from other compounds. Proline is unique among the 20 protein-forming amino acids because the amino group is secondary. The more common primary amino group is directly bonded to a carbon atom. In proline, the amino group is a secondary amine since it is bonded to two carbon atoms.

Structure

Proline is the only proteinogenic amino acid with a secondary amine, in that the nitrogen atom is connected to two alkyl groups, making it a secondary amine. The distinctive cyclic structure of proline's side chain locks its phi angle at approximately -75 degrees, giving the protein a defined structure.

Biosynthesis

In humans, proline is synthesized from glutamate. This process, which involves five enzymatic steps, converts glutamate to proline. The enzymes include glutamate 5-kinase, glutamate-5-semialdehyde dehydrogenase, and pyrroline-5-carboxylate reductase.

Function

Proline plays important roles in protein structure and metabolism. It is a major component of collagen, the connective tissue that supports most tissues and gives cells structure and firmness. Proline also helps break down proteins for use in creating new, healthy cells.

Dietary sources

Proline is found in many foods, especially in meat, dairy products, and eggs. It can also be found in some vegetables and grains, but in smaller amounts.

See also

• Amino acid
• Protein biosynthesis
• Collagen

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