This enzyme is involved in carotenoid biosynthesis and catalyses up to three desaturation steps (cf. EC 1.3.99.29 [phytoene desaturase (zeta-carotene-forming)], EC 1.3.99.30 [phytoene desaturase (3,4-didehydrolycopene-forming)], EC 1.3.99.31 [phytoene desaturase (lycopene-forming)]). The enzyme is activated by FAD. NAD+, NADP+ or ATP show no activating effect .
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The taxonomic range for the selected organisms is: Rhodobacter capsulatus The expected taxonomic range for this enzyme is: Bacteria, Archaea
This enzyme is involved in carotenoid biosynthesis and catalyses up to three desaturation steps (cf. EC 1.3.99.29 [phytoene desaturase (zeta-carotene-forming)], EC 1.3.99.30 [phytoene desaturase (3,4-didehydrolycopene-forming)], EC 1.3.99.31 [phytoene desaturase (lycopene-forming)]). The enzyme is activated by FAD. NAD+, NADP+ or ATP show no activating effect [1].
intermediates are phytofluene and zeta-carotene. The proportion of all-trans versus cis isomers is about 20% for phytofluene, 46% for zeta-carotene, and 72% for neurosporene
the enzyme belongs to the CrtI family of enzymes, analysis of the phylogenetic tree of a subset of phytoene desaturases from the CrtI family, overview. Recombinant expression of eight codon optimized CrtI enzymes from different clades in a bacterial system reveals that three CrtI enzymes can catalyse up to six desaturations, forming tetradehydrolycopene. Existence of characteristic patterns of desaturated molecules associated with various CrtI clades. Variations in the reaction rates and binding constants can explain the various carotene patterns observed. Relationship between genetic and functional evolution of certain CrtI enzymes, overview
carotenoid biosynthesis starts with the symmetrical condensation of two geranylgeranyl diphosphate molecules, forming phytoene. A series of successive desaturation reactions convert phytoene into phytofluene, zeta-carotene, neurosporene, lycopene. These desaturation reactions can be accomplished by a single enzyme (poly-trans pathway) or through a cascade of different enzymes (poly-cis pathway). In algae and plants, four different enzymes are necessary to form the final product (all-trans-lycopene). The phytoene and the zeta-carotene desaturases (PDS and ZDS, respectively) add double bonds in the cis-conformation. ZISO (zeta-carotene isomerase) and CRTISO (prolycopene isomerase) convert the cis-carotenes into di-cis-zeta-carotene and all-trans-lycopene, respectively. By contrast to other phytoene desaturases, CrtI are versatile enzymes classified into four enzymatic subgroups (EC 1.3.99.28, EC 1.3.99.29, EC 1.3.99.30, and EC 1.3.99.31) based on the last product they presumably produce (from zeta-carotene to didehydrolycopene). Carotene diversity can be further expanded in later steps with the addition of one or two rings by lycopene cyclases, thereby producing an extensive variety of symmetrical or asymmetrical cyclised carotenes, such as beta-zeacarotene, dehydro-beta-carotene, gamma-carotene, beta-carotene, and the fungi-specific torulene. When expressed in heterologous hosts, CrtI enzymes exhibit distinct desaturation patterns, CrtI enzyme activities may depend on the experimental conditions and thus be inconsistent with the patterns generated in the natural host. Rhodobacter capsulatus strain SB1003 also produces lycopene in vitro (cf. EC 1.3.99.31)
comparison of the natural evolution and kinetic properties of selected CrtI enzymes expressed and assayed under standardised conditions. Potentially all CrtI enzymes can catalyse desaturation reactions that progress beyond the already observed end-products and the pattern of products formed originates from variations in the reaction rates rather than affinity constants
competition between lycopene cyclase and the phytoene desaturases modified the distribution between carotene intermediates when expressed in yeast in the context of the full beta-carotene production pathway
gene crtI, phylogenetic tree, co-expression with 5 other enzymes of the carotenoid pathway from Pantoea agglomerans, i.e. IPP isomerase, FPP synthase, GGPP synthase, phytoene synthase, lycopene cyclase, beta-carotene hydrolase, and zeaxanthin glucosyltransferase, in Escherichia coli, functional complementation by CrtI of Brevibacterium linens, CGI, CrtI of Corynebacterium glutamicum, RSI, CrtI of Rhodobacter sphaeroides RCI, CrtI of Rhodobacter capsulatus, and RBI, CrtI of Rhodopirellula baltica, and the homologous complementation of CrtI from Pantoea agglomerans with the Pantoea agglomerans carotenogenic module expressing CrtEPAG -CrtBPAG
the phytoene desaturase gene, from Rhodobacter capsulatus is functionally complemented with a gene construct from Erwinia uredovora which encodes all enzymes responsible for formation of 15-cis phytoene in Escherichia coli
Characterization of the geranylgeranyl diphosphate synthase gene in Acyrthosiphon pisum (Hemiptera Aphididae) and its association with carotenoid biosynthesis