L-pipecolic acid metabolism in human liver: detection of L-pipecolate oxidase and identification of its reaction product.

L-Pipecolate oxidase, an enzyme that oxidizes L-pipecolic acid in the human liver has been demonstrated in the peroxisomal preparation. This enzyme oxidizes L-pipecolic acid with concomitant production of H2O2 in the peroxisome of the normal human liver. The immediate product of L-pipecolic acid oxidation has been identified as L-alpha-aminoadipate delta-semialdehyde. This reaction product was directly, and also after conversion to pipecolic acid by NaBH4 reduction, characterized by use of an amino acid analyzer and thin-layer chromatography. The pit fall of an indirect assay of L-pipecolate oxidase by means of the assay of alpha-aminoadipic acid formation was discussed.