THE VACUOLAR LOCALIZATION OF A BASIC PEROXIDASE ISOENZYME RESPONSIBLEFOR THE SYNTHESIS OF ALPHA-3',4'-ANHYDROVINBLASTINE IN CATHARANTHUS-ROSEUS (L) DON,G. LEAVES

Partially purified protein extracts of Catharanthus roseus leaves were able to couple catharanthine and vindoline to produce alpha-3',4'-anh ydrovinblastine (AVLB) in a reaction strictly dependent on H2O2. This result, and the co-purification of peroxidase with AVLB synthetase act ivity, strongly suggest a peroxidase-like nature for the coupling enzy me, Only one peroxidase isoenzyme was detected in C. roseus leaves, an d it was shown that this isoenzyme consists of a molecularly-heterogen eous basic peroxidase (EC 1 . 11 . 1 . 7) mainly located in the vacuol e, These results suggest that a basic peroxidase located in the vacuol e may be the main enzyme responsible for AVLB synthesis in C. roseus l eaves, This isoenzyme was also found in cell walls where a peroxidase inhibitor was detected.