TY - JOUR
T1 - Novel apocarotenoid intermediates in Neurospora crassa mutants imply a new biosynthetic reaction sequence leading to neurosporaxanthin formation
AU - Estrada, Alejandro F.
AU - Maier, Dominic
AU - Scherzinger, Daniel
AU - Avalos, Javier
AU - Al-Babili, Salim
PY - 2008/11/1
Y1 - 2008/11/1
N2 - Neurosporaxanthin, β-apo-4′-carotenoic acid (C35), represents the end-product of the carotenoid pathway in Neurospora crassa. It is supposed to be synthesized in three steps catalyzed by sequential AL-2, CAO-2 and YLO-1 activities: (i) cyclization of 3,4-didehydrolycopene (C40); (ii) cleavage of torulene into β-apo-4′-carotenal (C35); and finally (iii) oxidation of β-apo-4′-carotenal. However, analyses of the ylo-1 mutant revealed the accumulation of intermediates other than β-apo-4′-carotenal. Here, we generated a 3,4-didehydrolycopene accumulating Escherichia coli strain and showed that CAO-2 cleaves this acyclic carotene in vivo and in vitro yielding apo-4′-lycopenal. The apocarotenoids accumulated in the ylo-1 mutant were then identified as apo-4′-lycopenal and apo-4′-lycopenol, pointing to the former as the YLO-1 substrate and indicating that cyclization is the last step in neurosporaxanthin biosynthesis. This was further substantiated by analyses of a cyclase-deficient al-2 mutant, revealing the accumulation of apo-4′-lycopenoic acid. The three acyclic apocarotenoids presented here have not been found naturally before.
AB - Neurosporaxanthin, β-apo-4′-carotenoic acid (C35), represents the end-product of the carotenoid pathway in Neurospora crassa. It is supposed to be synthesized in three steps catalyzed by sequential AL-2, CAO-2 and YLO-1 activities: (i) cyclization of 3,4-didehydrolycopene (C40); (ii) cleavage of torulene into β-apo-4′-carotenal (C35); and finally (iii) oxidation of β-apo-4′-carotenal. However, analyses of the ylo-1 mutant revealed the accumulation of intermediates other than β-apo-4′-carotenal. Here, we generated a 3,4-didehydrolycopene accumulating Escherichia coli strain and showed that CAO-2 cleaves this acyclic carotene in vivo and in vitro yielding apo-4′-lycopenal. The apocarotenoids accumulated in the ylo-1 mutant were then identified as apo-4′-lycopenal and apo-4′-lycopenol, pointing to the former as the YLO-1 substrate and indicating that cyclization is the last step in neurosporaxanthin biosynthesis. This was further substantiated by analyses of a cyclase-deficient al-2 mutant, revealing the accumulation of apo-4′-lycopenoic acid. The three acyclic apocarotenoids presented here have not been found naturally before.
KW - Apocarotenoids
KW - Carotenoid biosynthesis
KW - Carotenoid cleavage
KW - Fungi
KW - Neurospora crassa
KW - Neurosporaxanthin
UR - http://www.scopus.com/inward/record.url?scp=55149118381&partnerID=8YFLogxK
U2 - 10.1016/j.fgb.2008.09.001
DO - 10.1016/j.fgb.2008.09.001
M3 - Article
C2 - 18812228
AN - SCOPUS:55149118381
VL - 45
SP - 1497
EP - 1505
JO - Fungal Genetics and Biology
JF - Fungal Genetics and Biology
SN - 1087-1845
IS - 11
ER -