Polyamine degradation in foetal and adult bovine serum

1. Using protein-separative chromatographic procedures and assays specific for putrescine oxidase and spermidine oxidase, adult bovine serum was found to contain a single polyamine-degrading enzyme with substrate preferences for spermidine and spermine. Apparent Km values for these substrates were approx. 40 microM. The apparent Km for putrescine was 2 mM. With spermidine as substrate, the Ki values for aminoguanidine (AM) and methylglyoxal bis(guanylhydrazone) (MGBG) were 70 microM and 20 microM respectively. 2. Bovine serum spermidine oxidase degraded spermine to spermidine to putrescine and N8-acetylspermidine to N-acetylputrescine. Acrolein was produced in all these reactions and recovered in quantities equivalent to H2O2 recovery. 3. Spermidine oxidase activity was present in foetal bovine serum, but increased markedly after birth to levels in adult serum that were almost 100 times the activity in foetal bovine serum. 4. Putrescine oxidase, shown to be a separate enzyme from bovine serum spermidine oxidase, was present in foetal bovine serum but absent from bovine serum after birth. This enzyme displayed an apparent Km for putrescine of 2.6 microM. The enzyme was inhibited by AM and MGBG with Ki values of 20 nM. Putrescine, cadaverine and 1,3-diaminopropane proved excellent substrates for the enzyme compared with spermidine and spermine, and N-acetylputrescine was a superior substrate to N1- or N8-acetylspermidine.