Premium
Cooperation of two carotene desaturases in the production of lycopene in Myxococcus xanthus
Author(s) -
Iniesta Antonio A.,
Cervantes María,
Murillo Francisco J.
Publication year - 2007
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2007.05960.x
Subject(s) - phytoene , myxococcus xanthus , phytoene desaturase , phytoene synthase , lycopene , isomerase , operon , carotenoid , biochemistry , chemistry , carotene , biology , gene , stereochemistry , biosynthesis , escherichia coli , food science , mutant
In Myxococcus xanthus , all known carotenogenic genes are grouped together in the gene cluster carB–carA , except for one, crtIb (previously named carC ). We show here that the first three genes of the carB operon, crtE , crtIa , and crtB , encode a geranygeranyl synthase, a phytoene desaturase, and a phytoene synthase, respectively. We demonstrate also that CrtIa possesses cis ‐to‐ trans isomerase activity, and is able to dehydrogenate phytoene, producing phytofluene and ζ‐carotene. Unlike the majority of CrtI‐type phytoene desaturases, CrtIa is unable to perform the four dehydrogenation events involved in converting phytoene to lycopene. CrtIb, on the other hand, is incapable of dehydrogenating phytoene and lacks cis ‐to‐ trans isomerase activity. However, the presence of both CrtIa and CrtIb allows the completion of the four desaturation steps that convert phytoene to lycopene. Therefore, we report a unique mechanism where two distinct CrtI‐type desaturases cooperate to carry out the four desaturation steps required for lycopene formation. In addition, we show that there is a difference in substrate recognition between the two desaturases; CrtIa dehydrogenates carotenes in the cis conformation, whereas CrtIb dehydrogenates carotenes in the trans conformation.