Biosynthesis of fucoxanthin and diadinoxanthin and function of initial pathway genes in Phaeodactylum tricornutum.
The biosynthesis pathway to diadinoxanthin and fucoxanthin was elucidated in Phaeodactylum tricornutum by a combined approach involving metabolite analysis identification of gene function. For the initial steps leading to β-carotene, putative genes were selected from the genomic database and the function of several of them identified by genetic pathway complementation in Escherichia coli. They included genes encoding a phytoene synthase, a phytoene desaturase, a ζ-carotene desaturase, and a lycopene β-cyclase. Intermediates of the pathway beyond β-carotene, present in trace amounts, were separated by TLC and identified as violaxanthin and neoxanthin in the enriched fraction. Neoxanthin is a branching point for the synthesis of both diadinoxanthin and fucoxanthin and the mechanisms for their formation were proposed. A single isomerization of one of the allenic double bounds in neoxanthin yields diadinoxanhin. Two reactions, hydroxylation at C8 in combination with a keto-enol tautomerization and acetylation of the 3'-HO group results in the formation of fucoxanthin.
Department of Molecular Bioscience, J.W. Goethe University  Frankfurt, Germany.
Michael
M
Dambek
Ulrike
U
Eilers
Jürgen
J
Breitenbach
Sabine
S
Steiger
Claudia
C
Büchel
Gerhard
G
Sandmann
D053898:Biosynthetic Pathways; D002338:Carotenoids / Q000737:chemistry / Q000378:metabolism; D017377:Diatoms / Q000737:chemistry / Q000201:enzymology / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase / Q000235:genetics / Q000378:metabolism; D019753:Intramolecular Lyases / Q000235:genetics* / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D024341:Xanthophylls / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D019207:beta Carotene / Q000737:chemistry / Q000378:metabolism; D024321:zeta Carotene / Q000737:chemistry / Q000378:metabolism
D024341:Xanthophylls; D024321:zeta Carotene; D019207:beta Carotene; C025164:fucoxanthin; C033808:diadinoxanthin; D002338:Carotenoids; C005613:violaxanthin; C100185:(all-E) phytoene; D010088:Oxidoreductases; C022398:phytoene dehydrogenase; C099215:zeta-carotene desaturase; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase; C011947:neoxanthin