The vacuolar localization of a basic peroxidase isoenzyme responsible for the synthesis of α-3',4'-anhydrovinblastine in Catharanthus roseus (L.) G. Don leaves.

Partially purified protein extracts of Catharanthus roseus leaves were able to couple catharanthine and vindoline to produce &alpha3'4'- anhydrovinblastine (AVLB) in a reaction strictly dependent on H2O2. This result, and the co-purification of peroxidase with AVLB synthetase activity, strongly suggest a peroxidase-like nature for the coupling enzyme. Only one peroxidase isoenzyme was detected in C. roseus leaves, and it was shown that this isoenzyme consists of a molecularly-heterogeneous basic peroxidase (EC 1.11.1.7) mainly located in the vacoule. This results suggest that a basic peroxidase located in the vacoule may be the main enzyme responsible for AVLB synthesis in C. roseus leaves. This isoenzyme was also found in cell walls where a peroxidase inhibitor was detected. [ABSTRACT FROM AUTHOR]