Delta-1-pyrroline-5-carboxylate

Delta-1-pyrroline-5-carboxylate (also known as P5C or 1-pyrroline-5-carboxylate) is a metabolite involved in several important biochemical pathways in the human body. It is an intermediate in both the proline and arginine biosynthesis pathways, and plays a crucial role in the cellular response to osmotic stress.

Structure and Properties

Delta-1-pyrroline-5-carboxylate is a cyclic amino acid derivative, with a five-membered ring structure. It has a carboxylate group at the 5-position, and a double bond between the 1- and 2-positions. This gives it a degree of aromaticity, which can influence its reactivity and interactions with other molecules.

Biosynthesis

P5C is synthesized from glutamate in a two-step process. First, glutamate is reduced to glutamate semialdehyde by the enzyme glutamate 5-kinase. This is then spontaneously converted to P5C.

In the reverse direction, P5C can be converted back to glutamate by the enzyme P5C dehydrogenase, in a reaction that also produces NADH.

Role in Proline and Arginine Biosynthesis

P5C is a key intermediate in the biosynthesis of the amino acids proline and arginine. In the proline biosynthesis pathway, P5C is reduced to proline by the enzyme P5C reductase, using NADH as a cofactor.

In the arginine biosynthesis pathway, P5C is first converted to ornithine by the enzyme ornithine aminotransferase. Ornithine is then converted to arginine via a series of reactions known as the urea cycle.

Role in Osmotic Stress Response

Under conditions of osmotic stress, cells can accumulate high levels of P5C, which can be converted to proline. Proline acts as a compatible solute, helping to maintain cell volume and protect cellular structures.

See Also

• Proline
• Arginine
• Glutamate
• Metabolite
• Biochemical pathway