A Newly-Detected Reductase from Rauvolfia Closes a Gap in the Biosynthesis of the Antiarrhythmic Alkaloid Ajmaline

Abstract

A new enzyme, 1,2-dihydrovomilenine reductase (E.C. 1.3.1), has been detected in Rauvolfia cell suspension cultures. The enzyme specifically converts 2β(R)-1,2-dihydrovomilenine through an NADPH-dependent reaction into 17-O-acetylnorajmaline, a close biosynthetic precursor of the antiarrhythmic alkaloid ajmaline from Rauvolfia. A five-step purification procedure using SOURCE 30Q chromatography, hydroxyapatite chromatography, 2′,5′-ADP Sepharose 4B affinity chromatography and ion exchange chromatography on DEAE Sepharose and Mono Q delivered a ∼ 200-fold enriched enzyme in a yield of ∼ 6 %. SDS-PAGE showed an M_r for the enzyme of ∼ 48 kDa. Optimum pH and optimum temperature of the reductase were at pH 6.0 and 37 °C. The enzyme shows a limited distribution in cell cultures expressing ajmaline biosynthesis, and is obviously highly specific for the ajmaline pathway.

Key words

Rauvolfia serpentina Benth. ex Kurz - Apocynaceae - cell suspension culture - 1,2-dihydrovomilenine reductase - ajmaline biosynthesis

References

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1 Shujuan Gao and Gerald von Schumann have contributed equally to this study.