Synthesis o f carotenoids is photoregulated in m any fungi including Neurospora crassa. In order to investigate the regulatory m echanism at the enzym e level, several carotenoid m utants o f Neurospora were used to determ ine the activities o f enzym es involved in the carotenoid b io­ synthetic pathway after growth under illum ination or in darkness. Light stim ulation o f caro­ tenoid form a...

Cell extracts from car mutants of Phycomyces blakesleeanus, which can convert '4C—labelled mevalonic acid into unsaturated carotenes, were treated with high ionic strength buffer and a range of detergents in an attempt to solubilise the carotenogenic enzymes. Phytoene synthetase was dislodged from the membrane with high molarity Tris-HC1 buffer, but the enzymes which convert phytoene into s—car...

Studies on models synthesized by stereochemically controlled routes show that the central triene chromophore in the common cis isomer of phytoene has the irans,cis,trans configuration, and that the phytoene from Flavobacterium dehydrogenans consists mainly of the all-trans isomer. Capsorubin, with the natural configuration at all four chiral centres, has been synthesized from (+)-camphor. Sever...

The herbicide norflurazon inhibits carotene biosynthesis in photosynthetic organisms by blocking the enzyme phytoene dehydrogenase (= phytoene desaturase). We have isolated norflurazon-resistant mutants of the cyanobacterium Synechococcus PCC7942. The herbicide-resistance gene from the mutant NFZ4 has been cloned by genetic complementation of the resistance trait in wild type cells. The experim...

The 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway leads to the synthesis of isopentenyl diphosphate in plastids. It is a major branch point providing precursors for the synthesis of carotenoids, tocopherols, plastoquinone and the phytyl chain of chlorophylls, as well as the hormones abscisic acid and gibberellins. Consequently, disruption of this pathway is harmful to plants. We developed a...

A non-radioactive cell-free assay was developed to quantitatively determine inhibition of plant-type phytoene desaturase by bleaching herbicides. An active desaturase was prepared from an appropriately cloned E. coli transformant. Another E. coli transformant was used to produce the required phytoene. Phytofluene and zeta-carotene, the products of the desaturase reaction, were either determined...

The incorporation of 12-14C,(5R)-5-3Hj]MVA* and 12-14C,5-3H2]MVA into geranylgeraniol and phytoene by a preparation of 'non-aqueous' bean leaf chloroplasts has been studied. In the formation of phytoene from two molecules of geranylgeranyl pyrophosphate, the loss of hydrogen is stereospecific, the hydrogen atom lost from C-1 of each molecule of geranylgeranyl pyrophosphate being that which was ...

Detailed studies of the properties of carotenoids isolated from diphenylamine-inhibited cultures of Rhodospirillum rubrum have revealed a number of novel structures which indicate new features of carotenoid biosynthesis in the photosynthetic bacteria. The dehydrogenation of phytoene to coloured carotenoids occurs by a sequence which is different from that in higher plants in that 7,8,11,12-tetr...

The partially purified phytoene synthetase enzyme complex obtained from tomato fruit plastids dissociates into two or more subunit species on chromatography in low ionic strength buffer on DEAE-cellulose. One of these subunits prelycopersene pyrophosphate synthetase, has a molecular weight of approximately 40,000, whereas the phytoene synthetase complex has a molecular weight of 200,000. The pr...