DEGUELIN CYCLASE, A PRENYL TO CHROMEN TRANSFORMING ENZYME FROM TEPHROSIA-VOGELLII

Seeds and plant parts of Tephrosia vogellii were investigated in order to provide systems for the study of prenyl to chromen transformation in rotenoids, as exemplified by the conversion of rot-2-enonic acid into deguelin. No hydroxylated intermediate was found. A cell free preparation has been obtained from T. vogellii seedlings or seeds and shown to catalyse the reaction. The water soluble enzyme has been partially purified using ammonium sulphate precipitation, gel chromatography and ion exchange procedures. Data for the enzyme, named deguelin cyclase, are reported-optima for pH and temperature and K(m) (which indicates strong binding between enzyme and substrate). Results relevant to M(r) determination are discussed. The enzyme has a requirement for oxygen, but not for cofactors. It is inhibited by chloride ion and chelating agents, particularly 1,10-phenanthroline. Deguelin cyclase can convert the 11-hydroxyrotenoid sumatrolic acid into alpha-toxicarol and lapachol into dehydro-alpha-lapachone, though the prenyl to chromen conversion is not general. It does not convert rot-2'-enonic acid into rotenone under the conditions studied. Deguelin cyclase seems not to belong to the P450 group and resembles more closely the non-heme iron protein isopenicillin N synthase.