Vinorine hydroxylase

Vinorine hydroxylase hydroxylates vinorine to form vom-ilene (88). Vinorine hydroxylase seems to be a P450 enzyme that requires an NADPH-dependent reductase. This enzyme is labile and has not been cloned yet. Next, the indolenine bond is reduced by an NADPH-dependent reductase to yield 1,2-dihydrovomilenene. A second enzyme, 1,2-dihydrovomilenene reductase, then reduces this product to... 

Ma X, Koepke J, Panjikar S, Eritzsch G, Stoeckigt J. Crystal estructure of vinorine synthase, the first representative of the BAHD superfamily. J. Biol. Chem. 2005 280 13576-13583. Ealkenhagen H, Polz L, Takayama H, Kitajima M, Sakai S, Aimi N, Stockigt J. Substrate specificity of vinorine hydroxylase, a... 

The enzyme which follows the vinorine synthase was commonly named vinorine hydroxylase. VH is responsible for the generation of vomiienine (29) by selective hydroxylation of vinorine (17) at the C-21 position (Figure 18). The reaction is catalyzed exclusively by a microsomal protein from Rauvolfia cultured cells in the presence of the substrate vinorine, NADPH, and O2. The investigation of the taxonomical distribution of the enzyme indicated that vinorine hydroxylase is exclusively present in ajmahne-producing plant cells. It was also observed that the substrate specificity of VH was high. Alkaloids with vinorine-related structures such as fJ-tetra-phyllicine or its Z-configurated isomer were not hydroxylated... 

Figure 18 Reaction step catalyzed by membrane-bound vinorine hydroxylase from Rauvolfia cell cultures leading from 17 to the hydroxylated 29.

Whereas vinorine hydroxylase catalyzes the first reaction (hydroxylation) taking place on the periphery of the ajmalan skeleton at C-21, the second and the third steps represent two hydrogenations. These reactions are performed by the NADPH-dependent soluble reductases, vomilenine reduc-... 

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