Catalyzes the hydrolysis of polyneuridine aldehyde into epi-vellosimine, which is the immediate precursor for the synthesis of ajmaline. H2O + polyneuridine aldehyde = 16-epivellosimine + CO2 + methanol Inhibited by DEPC and HgCl(2). Alkaloid biosynthesis; ajmaline biosynthesis. Homodimer; homodimerizes in aqueous solutions at pH 7.0. Ajmaline is an anti-arrhythmic alkaloid commercially used as an efficient drug for the treatment of arrhythmic heart disorder. Belongs to the AB hydrolase superfamily.