Carotenogenesis gene cluster and phytoene desaturase catalyzing both three- and four-step desaturations from  Rhodobacter azotoformans.
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.
State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong University, Jinan, China.
Jinhua
J
Zhang
Lili
L
Lu
Lijie
L
Yin
Shen
S
Xie
Min
M
Xiao
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000096:biosynthesis* / Q000378:metabolism; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005798:Genes, Bacterial; D005822:Genetic Vectors; D000077276:Lycopene; D005810:Multigene Family; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016992:Rhodobacter / Q000201:enzymology* / Q000235:genetics*
D001426:Bacterial Proteins; D011994:Recombinant Proteins; C005637:spheroidene; D002338:Carotenoids; C008604:neurosporene; C100185:(all-E) phytoene; D010088:Oxidoreductases; C022398:phytoene dehydrogenase; D000077276:Lycopene