6β-HYDROXYHYOSCYAMINE EPOXIDASE FROM CULTURED ROOTS OF HYOSCYAMUS NIGER

Article abstract of DOI:10.1016/0031-9422(89)80186-4

Enzyme preparations from cultured roots of Hyoscyamus niger converted 6β-hydroxyhyoscyamine to scopolamine in the presence of the co-factors required by 2-oxoglutarate-dependent dioxygenases, i.e. 2-oxoglutarate, ferrous ion and ascorbate.The epoxidase, a soluble enzyme, requires molecular oxygen for the reaction.Incubations with 6β-<6-(18)O>hydroxyhyoscyamine and 6β-hydroxy<7β-(2)H>hyoscyamine as substrates demonstrated that the epoxidation reaction proceeds with retention of the 6β-hydroxy oxygen and with loss of the 7β-hydrogen.The epoxidase activity found under the optimal reaction conditions studied was considerably lower than the activity of hyoscyamine 6β-hydroxylase in cultured roots, and the two activities could not be separated during partial purification.The function of this epoxidase in scopolamine biosynthesis is discussed in relation to hyoscyamine 6β-hydroxylase. - Keywords: Hyoscyamus niger; Solanaceae; biosynthesis; tropane alkaloids; 6β-hydroxyhyoscyamine; scopolamine; epoxidase.