Candida boidinii grows well on spermidine as sole nitrogen source, but poorly on spermine. Cells grown on spermidine, cadaverine, putrescine and 1,3-diaminopropane contained a polyamine oxidase which attacks spermine and spermidine at the secondary amino groups, forming putrescine and a product thought to be 3-aminopropionaldehyde. The enzyme was synthesized before growth began when that had been grown in medium containing glucose + ammonium was transferred to medium in which spermidine replaced ammonium. Other enzymes increasing in specific activity during this adaptation were catalase, benzylamine oxidase and N AD-dependent glutamate dehydrogenase. The polyamine oxidase was purified to 50% homogeneity, but was too unstable to obtain completely pure. It had a pH optimum of 10.0, and could be stabilized by addition of inert protein. It oxidized spermine, spermidine, acetylspermidine, -butylpropylamine, di--butylamine and di--hexylamine. It did not oxidize di--propylamine, diethylamine or , -diacetylspermidine. Apparent K values were determined for the active substrates. The enzyme was potently inhibited by quinacrine and by divalent cations. The stoicheiometry of the enzyme reaction was established using di--butylamine as substrate. The enzyme has a molecular weight in the range 80000 to 110000. Putrescine (the oxidation product of spermidine) was not oxidized by cell-free extracts, but evidence of aminotransferase activity was found. The oxidation/transamination product of putrescine, 4-aminobutyraldehyde (1-pyrroline), was oxidized by extracts and a scheme is presented by which spermidine could be catabolized. Polyamine oxidase was shown to co-sediment with NAD-dependent glycerol 3-phosphate dehydrogenase and catalase in sucrose gradients after mechanical breakage of spheroplasts, and is thus a peroxisomal enzyme. Polyamine oxidase was present in some other yeasts when grown on spermidine, and , but absent from and . These latter yeasts probably contained an enzyme resembling benzylamine/putrescine oxidase which attacks the primary amino groups of spermidine.


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