Preparation of dehydrobenzylisoquinolines by immobilized (S)-tetrahydroprotoberberine oxidase from plant cell cultures

Abstract ( S )-Tetrahydroprotoberberine oxidase (STOX) has been isolated in enriched (7.4-fold) form from a high yielding cell suspension of Berberis wilsoniae var. subcaulialata in a three step procedure and was immobilized by several different methods. The properties of immobilized STOX were compared with immobilized Berberis cells and with the soluble enzyme. Although pH and temperature optima were shifted by immobilization, K m -values with ( S )-norreticuline remained unaffected. The stability of immobilized STOX was 50 times better than the free enzyme. A cyclic process is described using the stereospecific enzymatic oxidation of ( S )norreticuline to 1,2-dehydronorreticuline followed by sodium borohydride reduction for the transformation of racemic norreticuline to the ( R )-enantiomer.