The reaction mechanism of chromanol-ring formation catalyzed by tocopherol cyclase from Anabaena variabilis Kutzing (Cyanobacteria)

Article abstract of DOI:10.1002/hlca.19940770705

Incubation of the synthetic ¹⁸O-labelled phytyl-hydroquinone (O⁴-¹⁸O)-2 with the tocopherol cyclase from Anabaena variabilis Kutzing (Cyanobacteria) in D₂O furnished the doubly labelled γ-tocopherol, (2R,3S,4'R,8'R)-(1-¹⁸O,3-²H)-1. The chirality at C(3) was determined by two independent routes providing interlocking evidence that the enzyme-catalyzed ring closure proceeds by si-protonation of the double bond of 2 and concomitant re-attack of the phenolic O-atom.