Molecular oxygen and the state of geometric isomerism of intermediates are essential in the carotene desaturation and cyclization reactions in daffodil chromoplasts.

摘要: The membrane-bound carotenogenic reaction sequence in daffodil chromoplasts can be subdivided vitro into three segments by varying the incubation parameters O2 and light. In first segment, 15-cis-phytoene is desaturated to 15-cis-ζ-carotene (trans elimination of hydrogen) dark presence as an essential cofactor. A photoisomerization 15-cis double bond accumulated ζ-carotene trans prerequisite for function second desaturation 7,9,9′,7′-tetra-cis-lycopene (prolycopene, cis hydrogen). role electron acceptor discussed evidence oxidoreductase acting a redox mediator between desaturase (forming polyene chromophore) presented. certain analogy stearoyl-carrier protein, which also occurs plastids, proposed. third cyclization prolycopene, active only absence involves additional cis-trans isomerization reactions.