Phytoene dehydrogenase

LCTKE-BRINKHAUS, F., LIEDVOGEL, B., KREUZ, K., KLEINIG, H., Phytoene synthase and phytoene dehydrogenase associated with envelope membranes from spinach chloroplasts, Planta 1982,156, 176-180. 

Fig. 8.16 Pathways for the production of hydroxylated carotenoids in . coli. Isopentenyl pyrophosphate (IPP) and farnesyl diphosphate (FPP) are produced via internal methylerythritol phosphate (MEP) pathway and FPP synthase. CrtE GGPP synthase, CrtB phytoene synthase, CrtI phytoene dehydrogenase, LycB lycopene p-cyclase, LycE lycopene e-cyclase...

Chromoplasts are ideal organelles for the study of carotene biosynthesis. The question arises what about chloroplasts in which in vivo apparently a carotenoid biosynthesis takes place. When chloroplasts or chloroplast subfractions are incubated in the presence of C-14 IPP a wide palette of prenyllipids is formed with the exception of carotenes (Table 2). Onyl in highly purified envelope fractions with very low contaminating chlorophyll synthase activities some phytoene synthase, phytoene dehydrogenase and cis-phytofluene isomerase activities have been described, when geranyIgerany1 pyrophosphate, not IPP, was provided as the substrate (ref. 23). 

A multienzyme aggregate of four identical dehydrogenases (copies of the car B gene product) that act sequentially in the conversion of phytoene into lycopene has been proposed to account for the formation of acyclic carotenoids in P. blakesleeanus... 

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