Carotenogenesis gene cluster and phytoene desaturase catalyzing both three- and four-step desaturations from Rhodobacter azotoformans

Abstract

A carotenogenesis gene cluster from the purple nonsulfur photosynthetic bacterium Rhodobacter azotoformans CGMCC 6086 was cloned. A total of eight carotenogenesis genes ( crtA , crtI , crtB , tspO , crtC , crtD , crtE , and crtF ) were located in two separate regions within the genome, a 4.9 kb region containing four clustered genes of crtAIB - tspO and a 5.3 kb region containing four clustered genes of crtCDEF . The organization was unusual for a carotenogenesis gene cluster in purple photosynthetic bacteria. A gene encoding phytoene desaturase ( CrtI ) from Rba. azotoformans was expressed in Escherichia coli. The recombinant CrtI could catalyze both three- and four-step desaturations of phytoene to produce neurosporene and lycopene, and the relative contents of neurosporene and lycopene formed by CrtI were approximately 23% and 75%, respectively. Even small amounts of five-step desaturated 3,4-didehydrolycopene could be produced by CrtI . This product pattern was novel because CrtI produced only neurosporene leading to spheroidene pathway in the cells of Rba. azotoformans. In the in vitro reaction, the relative content of lycopene in desaturated products increased from 19.6% to 62.5% when phytoene reduced from 2.6 to 0.13 μM. The results revealed that the product pattern of CrtI might be affected by the kinetics.

A unique low light adaptation mechanism inRhodobacter azotoformans

“…Recently, the CrtI from Rba. azotoformans was also found to be capable of catalyzing both three-and four-step desaturations of phytoene to produce neurosporene and lycopene in vitro [37]. Our results demonstrated that CrtI could catalyze both three-and four-step desaturations of phytoene in vivo to produce neurosporene and lycopene in Rba.…”

Current and Potential Natural Pigments From Microorganisms (Bacteria, Yeasts, Fungi, Microalgae)

“…In conjunction with the four-step phytoene desaturase that yields lycopene, a five-step desaturase was used to produce 3,5-didehydrolycopene (Zhang et al, 2012). Instead, carotenogenic genes from different bacteria are combined employing unique pathways that maintain altered product specificities in a simple E. coli host expressing the biosynthetic machinery for phytoene production.…”

Reconstruction of the Carotenoid Biosynthetic Pathway of Cronobacter sakazakii BAA894 in Escherichia coli

“…The first type has the classical organization of crtEXYIBZ , the second type has an organization of crtE-idi-crtXYIBZ , and the third type has an organization of crtE-idi-crtYIBZ . Although different microorganisms contain the similar gene cluster, they could produce different carotenoids [5]–[8]. This might depend on their living environment, because carotenoids with different structures show different effect on membrane fluidity and thermo stability [9].…”