Schizosaccharomyces pombe ODC active crude extracts were prepared as follows: S.pombe (strain 1519, leu1-32, h ± ) provided by R.Rowley was grown to OD 600 0.7 in 50 ml of minimal media + LEU. Ten milligrams of lysing enzymes (Sigma) were added, followed by continued incubation for 30 min at 30°C. Cells were harvested and washed once with cold homogenization buffer [25 mM Tris±HCl pH 7, 0.25 M sucrose, 1 mM dithiothreitol (DTT), 20 mM pyridoxal-5-phosphate, 2 mM EDTA] then resuspended in 0.75 ml of homogenization buffer. Cells were broken open and the lysate was clari®ed by centrifugation at 10 000 r.p.m. for 15 min at 4°C. Extracts were dialyzed overnight in dialysis buffer (25 mM Tris± HCl pH 7.4, 1 mM DTT, 20 mM pyridoxal-5-phosphate, 0.1 mM EDTA). A volume of 25 ml of extract was used for each ODC assay. ODC activity was assayed by measuring the release of 14 CO 2 from L-[1-14 C]ornithine (Amersham) as described (Nishiyama et al., 1988) . Each reaction took 1 h. Pre-incubation of S.pombe extract with 0.1 mM di¯uoromethyl ornithine (DFMO) for 15 min led to >99% inhibition of 14 CO 2 release.