Polyamine oxidase from Acanthamoeba culbertsoni specific for N8-acetylspermidine

Polyamine oxidase plays a key role in the catabolism of polyamines and regeneration of spermidine and putrescine. The mammalian enzyme utilises N1-acetylspermidine, and N8-acetylspermidine, although formed in the mammals, is not catabolised further. We have characterised an enzyme from Acanthamoeba culbertsoni which acts preferentially on N8-acetylspermidine. The highly unstable enzyme was stabilised in the presence of glycerol or dimethylsulphoxide together with spermine and purified 400-fold by a combination of DEAE-cellulose, CM-cellulose, spermine-Sepharose and Sephacryl S-300 chromatography. The enzyme has a pH optimum of 8 and a temperature optimum of 45 degrees C. The relative activities on different substrates are: N8-acetylspermidine 100%, N1-acetylspermine 40%, N1-acetylspermidine 1%, N1,8-diacetylspermidine 1% and N1,12-diacetylspermine 15%. Free polyamines and substrates of monoamine oxidase were not attacked. The enzyme yielded diaminopropane as an end product of catabolism and could be involved in the biosynthesis of this unusual polyamine present in large amounts in this organism.