PUTRESCINE OXIDATION IN MICROBODIES OF HELIANTHUS-TUBEROSUS TUBER

The subcellular localization of diamine oxidase activity (DAO, EC 1.4. 3.6) in Helianthus tuberosus tubers was further investigated. Microbod ies and mitochondria were isolated, using the same Percoll gradient, f rom tubers during dormancy (November-January) and at the break of dorm ancy (March), and DAO activity was checked in both organelle fractions . In microbodies the putrescine oxidizing activity was initially twice that of mitochondria, then decreased to values below those of mitocho ndria in March. In both cases the activity declined throughout the per iod examined, but in mitochondria activity increased in March. While t he putrescine oxidizing activity associated with microbodies was not a ffected by known inhibitors of diamine oxidase, that of mitochondria w as inhibited by methylglyoxal-bis(guanylhydrazone) (MGBG). A different role for the two organelles in the physiological stages examined is h ypothesized. The opening of new perspectives in the study of polyamine compartmentation and transport is also discussed.