Polyneuridine Aldehyde Esterase

Polyneuridine Aldehyde is an important enzyme during Ajmaline Biosynthesis, transforming C-10 skeleton polyneuridine aldehyde into C-9 skeleton epi-vellosimine. For the biochemical characterization of PNAE, the enzyme was isolated from plant cell cultures of the Indian medicinal plant Rauvolfia serpentina and partially sequenced; the PNAE cDNA was then cloned and overexpressed in Escherichia coli. PNAE showed extremely high specificity for its natural substrate, polyneuridine aldehyde,out of 14 alkaloidal and aromatic esters only polyneuridine aldehyde and its ethylester were processed. Sequence analysis led to the preliminary classification of PNAE as a new candidate of the large a/b hydrolase superfamily. This classification is based in particular on the catalytic triad Ser87, Asp216, and His244, which was previously verified by single mutations and homology modeling.