In wild-type S.pombe cells the most abundant polyamine is spermidine followed by putrescine ( Figure 3 ). Spermine and cadaverine are found in much smaller amounts. This distribution of polyamine content is very similar to that in other fungi for which polyamine concentrations have been measured (for references, see review by Tabor and Tabor, 1985) . The effect of SPA deletion on cellular polyamine contents was examined in both exponentially growing and stationary phase cells ( Figure 3 ). The cellular concentrations of putrescine, spermidine and cadaverine (but not spermine) were higher in the knockout strains than in wild-type cells. The greatest effect was seen on putrescine and cadaverine content, with smaller effects on spermidine, presumably because eukaryotic ODC activity directly catalyzes decarboxylation of both ornithine and lysine to produce putrescine and cadaverine, respectively (Pegg and McGill, 1979) , but subsequent regulatory events affect homeostasis of spermidine and spermine. The effect of inactivating antizyme on the polyamine contents in exponentially growing cells is modest (<2-fold in all cases). The effect becomes very pronounced in cells in stationary phase with up to 40-and 10-fold increases of putrescine and cadaverine contents, respectively, in the knockout strains.