Oxidation of spermidine and spermine in rat liver: purification and properties of polyamine oxidase

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Abstract
A novel enzyme responsible for the oxidation of spermidine and spermine was found in rat liver. Spermidine is degraded to putrescine and 3-aminopropionaldehyde, and spermine is cleaved to spermidine and 3-aminopropionaldehyde. A single enzyme catalyzing both reactions and designated as polyamine oxidase was purified 4000-fold to electrophoretic homogeneity. Polyamine oxidase appears to be a flavoprotein, containing FAD as a prosthetic group. H2O2 is evolved in the reaction and no other electron acceptors except O2 were found. The MW of the enzyme was .apprx. 60,000 and the sedimentation coefficient 4.5 S. The enzyme appears to be a single polypeptide chain since no evidence for structural subunits was obtained. Polyamine oxidase was sensitive to sulfhydryl and carbonyl group reagents. The optimum pH value for the oxidation of polyamines was close to 10. The reaction velocities were enhanced by various aldehydes, especially certain aromatic aldehydes. Polyamine oxidase appears to be localized in peroxisomes of liver cells, although the existence of an isoenzyme in the cytosolic fraction was not definitively ruled out. No marked changes were observed in the activity of polyamine oxidase in rat liver after partial hepatectomy, CCl4 and after treatment with growth hormone or thioacetaminde, conditions which are known to alter profoundly the metabolism and accumulation of polyamines.