Skip to main content
ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #333427
Title: Structural and biochemical characterization of cinnamoyl-coa reductases

Author
item SATTLER, STEVEN - Washington State University
item WALKER, ALEXANDER - Washington State University
item VERMERRIS, WILFRED - University Of Florida
item Sattler, Scott
item KANG, CHULHEE - Washington State University

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2016
Publication Date: 2/1/2017
Publication URL: https://handle.nal.usda.gov/10113/5763102
Citation: Sattler, S.A., Walker, A.M., Vermerris, W., Sattler, S.E., Kang, C. 2017. Structural and biochemical characterization of cinnamoyl-coa reductases. Plant Physiology. 173(2):1031-1044. doi:10.1104/pp.16.01671.

Interpretive Summary: In the US, sorghum biomass (stalks and leaves) serves as an important forage crop for livestock. In addition, sorghum is being developed as a bioenergy crop for advanced or 2nd generation biofuels production. Advanced biofuels are derived from the breakdown of the cellulose and hemicellulose components of biomass into sugars, and their subsequent conversion into biofuel molecules. A third biomass component, lignin, impedes breakdown of biomass in either livestock digestive systems or bioenergy conversion processes. Cinnamoyl-CoA reductase (CCR) gene encodes an enzyme involved in the synthesis of lignin. This study examined how this enzyme makes precursors to lignin. In sorghum, two classes of CCR enzymes were discovered, which have different roles in lignin synthesis. Second class of CCR enzymes is involved in making a specific type of lignin associated with plant defenses against pathogens. Collectively, this research gives a new perspective on the dual functions of this enzyme in lignin synthesis, and may lead to ways to protect plants from pathogens. In addition, this study potentially also provides new ways alter biomass composition of sorghum and other grasses to improve bioenergy conversion.

Technical Abstract: Cinnamoyl-coenzyme A reductase (CCR) catalyzes the reduction of hydroxycinnamoyl-coenzyme A (CoA) esters using NADPH to produce hydroxycinnamyl aldehyde precursors in lignin synthesis. The catalytic mechanism and substrate specificity of cinnamoyl-CoA reductases from sorghum (Sorghum bicolor), a strategic plant for bioenergy production, were deduced from crystal structures, site-directed mutagenesis, and kinetic and thermodynamic analyses. Although SbCCR1 displayed higher affinity for caffeoyl-CoA or p-coumaroyl-CoA than for feruloyl-CoA, the enzyme showed significantly higher activity for the latter substrate. Through molecular docking and comparisons between the crystal structures of the Vitis vinifera dihydroflavonol reductase and SbCCR1, residues threonine-154 and tyrosine-310 were pinpointed as being involved in binding CoA-conjugated phenylpropanoids. Threonine-154 of SbCCR1 and other CCRs likely confers strong substrate specificity for feruloyl-CoA over other cinnamoyl-CoA thioesters, and the T154Y mutation in SbCCR1 led to broader substrate specificity and faster turnover. Through data mining using our structural and biochemical information, four additional putative CCR genes were discovered from sorghum genomic data. One of these, SbCCR2, displayed greater activity toward p-coumaroyl-CoA than did SbCCR1, which could imply a role in the synthesis of defense-related lignin. Taken together, these findings provide knowledge about critical residues and substrate preference among CCRs and provide, to our knowledge, the first three-dimensional structure information for a CCR from a monocot species.