pipecolate

Pipecolic acid, or pipecolate, is a non-proteinogenic amino acid with the structure of piperidine-2-carboxylic acid. It features a six-membered piperidine ring bearing a carboxyl group and a ring nitrogen, making the molecule a zwitterion at physiological pH. This small cyclic amino acid occurs in trace amounts in plants and animals and is also encountered in various microbial contexts.

Biosynthesis and occurrence: Pipecolic acid arises chiefly through the lysine catabolic pathway known as the pipecolate pathway. In mammals, lysine can be converted through a series of transformations to form pipecolic acid, with the ring closure and subsequent steps producing the final product. It can also be generated by gut microbiota from lysine and related metabolites. Because of its presence in biological systems, pipecolic acid is routinely measured in metabolic studies and clinical tests.

Biological role and clinical relevance: Pipecolic acid is not incorporated into body proteins. Its physiological function is not fully understood, but it is recognized as a metabolite of lysine metabolism. Clinically, pipecolic acid is used as a biomarker in metabolomics and newborn/diagnostic investigations; elevated levels in urine or plasma are associated with peroxisomal disorders such as Zellweger spectrum disorders and related conditions, reflecting perturbations in lysine degradation and peroxisomal function.

Applications and properties: In addition to its biological context, pipecolic acid serves as a versatile building block in organic synthesis for piperidine-containing compounds, including pharmaceutical and natural product chemistry. It is water-soluble and forms salts with bases, facilitating handling in laboratory settings.