Pipecolic acid is oxidized by renal and hepatic peroxisomes: Implications for Zellweger's cerebro-hepato-renal syndrome (CHRS)

Abstract

Increased levels of pipecolic acid have been reported in patients with cerebro-hepatorenal syndrom (CHRS) of Zellweger and the general deficiency of peroxisomal function has been implicated in its pathogenesis. We have therefore investigated the capacity of normal peroxisomes to metabolize pipecolic acid. Highly purified peroxisomes were obtained from rat liver and rat and beef kidney cortex by a recently developed method using metrizamide gradients and a vertical rotor. These preparations oxidized d,l-pipecolic acid as evidenced by the measurement of H 2O 2 production. Incubation with either the d- or l-isomer revealed that almost exclusively d-pipecolate is oxidized. The specific activities proved to be 20–50 times higher in renal than in hepatic peroxisomes. A commercially available crystalline suspension of d-amino acid oxidase from porcine kidney also oxidized the pipecolic acid with the following rates 54:36:1 respectively for d-:, d,l-: l-isomers. Incubation of vibratome sections of rat kidney and liver in a medium containing d-pipecolic acid and cerous ions, revealed electron-dense deposits over the matrix of peroxisomes confirming the localization also by fine structural cytochemistry. These observations demonstrate the capability of mammalian peroxisomes to oxidize pipecolic acid and suggest that the absence or deficiency of peroxisomal d-amino acid oxidase may be implicated in the pathogenesis of hyperpipecolatemia in Zellweger's CHRS.