Biochemical characterization of a cinnamoyl-CoA reductase from wheat.
Cinnamoyl-CoA reductase (CCR) is responsible for the CoA ester-->aldehyde conversion in monolignol biosynthesis, which can divert phenylpropanoid-derived metabolites into the biosynthesis of lignin. To gain a better understanding of lignin biosynthesis in wheat (Triticum aestivum L.), a cDNA encoding CCR was isolated and named Ta-CCR2. DNA hybridization analyses demonstrated that the Ta-CCR2 gene exists in three copies in the wheat genome. RNA blot hybridization indicated that Ta-CCR2 was expressed most abundantly in root and stem tissues that were in the process of lignification. The secondary and three-dimensional structures of Ta-CCR2 were analyzed by molecular modeling. Recombinant Ta-CCR2 protein purified from E. coli converted feruloyl CoA, 5-OH-feruloyl CoA, sinapoyl CoA and caffeoyl CoA with almost similar efficiency, suggesting that it is involved in both G and S lignin synthesis. Ta-CCR2 had a very low V max value for 4-coumaroyl CoA, which may serve as a mechanism to control metabolic flux to H lignin in vivo . Furthermore, the reaction mechanism of Ta-CCR2 was analyzed in relation to its possible three-dimensional structure. The activity of Ta-CCR2 in relation to lignin biosynthesis is discussed.
Ma
Qing-Hu
QH
Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China. mqh@ibcas.ac.cn
Tian
Bin
B
D000214:Acyl Coenzyme A / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D015723:Gene Library; D008031:Lignin / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology; D018517:Plant Roots / Q000201:enzymology; D018547:Plant Stems / Q000201:enzymology; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D018749:RNA, Plant / Q000032:analysis / Q000378:metabolism; D014908:Triticum / Q000201:enzymology* / Q000235:genetics
D000214:Acyl Coenzyme A; D018744:DNA, Plant; D012333:RNA, Messenger; D018749:RNA, Plant; D008031:Lignin; D000445:Aldehyde Oxidoreductases; C019904:cinnamoyl CoA reductase