This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Terpenoids Biosynthesis → Tetraterpenoids Biosynthesis → Apocarotenoids Biosynthesis|
Some taxa known to possess this pathway include : Neurospora crassa
Expected Taxonomic Range: Opisthokonta
Apocarotenoids are terpenoid pigments derived from carotenoid pathways, they usually pigment organisms in bright yellow to orange color. They are products of carotenoid cleavage reactions generally mediated by carotenoid oxygenases. These enzymes constitute a new non-heme iron enzyme family found in all taxa [Sandmann08].
The apocarotenoids perform several important functions in organisms such as the retinal chromophore in fungi, the plant hormone, ABA, and the fungal pheromone, trisporic acid. The pigmentation of fungal and plant parts is due to the accumulation of apocarotenoids [Estrada08].
Neurosporaxanthin is a β-apo-4'-carotenoid (C35) that represents the end-product of the carotenoid pathway in Neurospora crassa. Neurosporaxanthin biosynthesis requires the activity of the albino gene products (AL-1, AL-2 and AL-3), which yield torulene [Estrada08a].
Neurosporaxanthin is synthesized in three sequential steps. The order of these steps was initially thought to consist of cyclization of all-trans-3,4-didehydrolycopene (C40), cleavage of the product, torulene, to form 4'-apo-β-carotenal (C35) [Saelices07], and oxidation of 4'-apo-β-carotenal as the final step. However, the isolation of mutants lacking these enzymes showed an accumulation of intermediates other than β-apo-4'-carotenal. The compounds were identified as apo-4'-lycopenal and apo-4'-lycopenol, indicating the presence of an alternative pathway, in which cyclization is the last step [Estrada08].
Estrada08: Estrada AF, Maier D, Scherzinger D, Avalos J, Al-Babili S (2008). "Novel apocarotenoid intermediates in Neurospora crassa mutants imply a new biosynthetic reaction sequence leading to neurosporaxanthin formation." Fungal Genet Biol 45(11);1497-505. PMID: 18812228
Estrada08a: Estrada AF, Youssar L, Scherzinger D, Al-Babili S, Avalos J (2008). "The ylo-1 gene encodes an aldehyde dehydrogenase responsible for the last reaction in the Neurospora carotenoid pathway." Mol Microbiol 69(5);1207-20. PMID: 18627463
Saelices07: Saelices L, Youssar L, Holdermann I, Al-Babili S, Avalos J (2007). "Identification of the gene responsible for torulene cleavage in the Neurospora carotenoid pathway." Mol Genet Genomics 278(5);527-37. PMID: 17610084
DiazSanchez11: Diaz-Sanchez V, Estrada AF, Trautmann D, Al-Babili S, Avalos J (2011). "The gene carD encodes the aldehyde dehydrogenase responsible for neurosporaxanthin biosynthesis in Fusariuma fujikuroi." FEBS J 278(17);3164-76. PMID: 21749649
Hausmann00: Hausmann A, Sandmann G (2000). "A single five-step desaturase is involved in the carotenoid biosynthesis pathway to beta-carotene and torulene in Neurospora crassa." Fungal Genet Biol 30(2);147-53. PMID: 11017770
PradoCabrero07: Prado-Cabrero A, Estrada AF, Al-Babili S, Avalos J (2007). "Identification and biochemical characterization of a novel carotenoid oxygenase: elucidation of the cleavage step in the Fusarium carotenoid pathway." Mol Microbiol 64(2);448-60. PMID: 17493127
Schmidhauser90: Schmidhauser TJ, Lauter FR, Russo VE, Yanofsky C (1990). "Cloning, sequence, and photoregulation of al-1, a carotenoid biosynthetic gene of Neurospora crassa." Mol Cell Biol 10(10);5064-70. PMID: 2144609
Schmidhauser94: Schmidhauser TJ, Lauter FR, Schumacher M, Zhou W, Russo VE, Yanofsky C (1994). "Characterization of al-2, the phytoene synthase gene of Neurospora crassa. Cloning, sequence analysis, and photoregulation." J Biol Chem 269(16);12060-6. PMID: 8163509
Schmulling03: Schmulling T, Werner T, Riefler M, Krupkova E, Bartrina y Manns I (2003). "Structure and function of cytokinin oxidase/dehydrogenase genes of maize, rice, Arabidopsis and other species." J Plant Res 116(3);241-52. PMID: 12721786
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