Kinetic Properties of Fungal Polyamine Oxidases and Their Application to Differential Determination of Spermine and Spermidine

Polyamine oxidase from Penicillium chrysogenum oxidized spermine rapidly and spermidine slightly at pH 7.5. The apparent Km values for spermine and spermidine were calculated to be 2.25×10-5M and 9.54×10-6M, respectively. The relative maximum velocities for spermine and spermidine were 3.37×10-3M (H2O2) per min per mg of protein and 2.08×10-4M (H2O2) per min per mg of protein, respectively. Spermine oxidation of the enzyme was competitively inhibited by spermidine and putrescine. The apparent Ki values by spermidine and putrescine were calculated to be 3.00×10-5M and 1.80×10-3M, respectively. On the other hand, polyamine oxidase from Aspergillus terreus rapidly oxidized both spermidine and spermine at pH 6.5. The apparent Km values for spermidine and spermine were 1.20×10-6M and 5.37×10-7M, respectively. The relative maximum velocities for spermidine and spermine were 1.55×10-2M (H2O2) per min per mg of protein and 6.20×10-3M (H2O2) per min per mg of protein, respectively. Differential determination of spermine and spermidine was carried out using the two enzymes. The initial rate was assayed with Penicillium enzyme and the end point was measured afte addition of Aspergillus enzyme. Small amounts of polyamines (25 to 200 nmol of spermine and 25 to 250 nmol of spermidine) were assayed by solving two simultaneous equations obtained from the rate assay method and the end point assay method. The calculated values were in close agreement with those obtained by an amino-acid analyzer.