Skip to main content
ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #370927

Research Project: Genetic Improvement of Sorghum for Bioenergy, Feed, and Food Uses

Location: Wheat, Sorghum and Forage Research

Title: Structure and function of the cytochrome P450 monooxygenase cinnamate 4-hydroxylase from sorghum bicolor1

item ZHANG, BIXIA - Washington State University
item LEWIS, KEVIN - Washington State University
item ABRIL, ALEJANDRA - University Of Florida
item DAVYDOV, DMITRI - 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: 4/9/2020
Publication Date: 7/1/2020
Citation: Zhang, B., Lewis, K.M., Abril, A., Davydov, D.R., Vermerris, W., Sattler, S.E., Kang, C. 2020. Structure and function of the cytochrome P450 monooxygenase cinnamate 4-hydroxylase from sorghum bicolor1. Plant Physiology. 183:957-973.

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. Biomass is composed nearly, entirely of plant cell walls, and lignin, a cell wall component makes these cells resistant to breakdown into their constituents that can be converted to biofuels and green chemicals. Cinnamate 4-hydroxylase is an enzyme that plays a central role in lignin synthesis. USDA-ARS and its university collaborators determined the structure of this critical enzyme for the first time ever. Resolving the structure of this enzyme provides researchers with greater understanding how this enzyme functions in the synthesis of lignin and other compounds derived from the amino acids, phenylalanine and tyrosine. In addition, a binding site on the surface of the enzyme identified in this study may provide insight into how this enzyme is regulated. This research provides a basis to redesign lignin in plants for livestock and bioenergy uses.

Technical Abstract: Cinnamate 4-hydroxylase (C4H, CYP73A) is a cytochrome P450 monooxygenase associated externally with endoplasmic reticulum of plant cells. The enzyme uses NADPH-cytochrome P450 reductase (CPR) as a donor of electrons and hydroxylates cinnamic acid to form 4- coumaric acid in phenylpropanoid metabolism. In order to better understand the structure and function of this unique class of plant P450 enzymes we have characterized the enzyme C4H1 from lignifying tissues of sorghum, encoded by Sobic.002G126600. Here we report the 1.7 Å resolution crystal structure of CYP73A33, the first X-ray structure of a plant C4H enzyme. The obtained structural information along with the results of the steady state kinetic analysis and the absorption spectroscopy titration displays a high degree of similarity of both the structural and functional features of C4H with other P450 proteins. Our data also suggest the presence of a putative allosteric substrate-binding site in a hydrophobic pocket on the enzyme surface. In addition, comparing the newly resolved structure with those of well investigated cytochromes P450 from mammals and bacteria enabled us to identify the residues of critical functional importance, and revealed a unique sequence signature that is potentially responsible for substrate specificity and catalytic selectivity of C4H.