Location: Wheat, Sorghum and Forage ResearchTitle: Activity of cytosolic ascorbate peroxidase (APX) from panicum virgatum against ascorbate and phenylpropanoids
|ZHANG, BIXIA - Washington State University|
|LEWIS, JACOB - Washington State University|
|KOVACS, FRANK - University Of Nebraska|
|KANG, CHULHEE - Washington State University|
Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2023
Publication Date: 1/16/2023
Citation: Zhang, B., Lewis, J., Kovacs, F., Sattler, S.E., Sarath, G., Kang, C. 2023. Activity of cytosolic ascorbate peroxidase (APX) from panicum virgatum against ascorbate and phenylpropanoids. International Journal of Molecular Sciences. 24.Article 1778. https://doi.org/10.3390/ijms24021778.
Interpretive Summary: Frequently, environmentally-induced stress causes an increase in oxidizing molecules, collectively termed reactive oxygen species (ROS), which includes hydrogen peroxide. Excess ROS can damage DNA, RNA, proteins and other key cellular components. To counteract the deleterious effects of ROS, plants synthesize a variety of enzymes and compounds that can inactivate excess ROS. One such enzyme is called ascorbate peroxidase, and it uses ascorbic acid (vitamin C) to remove hydrogen peroxide. Thus, both ascorbate peroxidase and ascorbate are critical to the health of plant cells. In this study, a specific switchgrass ascorbate peroxidase, PviAPX was structurally and biochemically characterized. The biochemical studies indicate that ascorbate peroxidase could also be involved in the biosynthesis of the plant cell wall component lignin. Using data generated by this study, future investigations will focus on the possible role for ascorbate peroxidase in switchgrass cell wall fortification.
Technical Abstract: APX is a key antioxidant enzyme in higher plants, scavenging H2O2 with ascorbate in several cellular compartments. Here we report the crystal structures of cytosolic ascorbate peroxidase from switchgrass (Panicum virgatum L., Pvi), a strategic feedstock plant with several end uses. The overall structure of PviAPX was similar to the structures of other APX family members with bound ascorbate molecule at the '-heme edge pocket as in other APX enzymes. Our results indicated that the H2O2-dependent oxidation of ascorbate displayed positive cooperativity. Significantly, our study suggested that PviAPX has the ability to oxidize a broad range of phenylpropanoids with d-meso site in a rather similar efficiency, which reflects its role in the fortification of cell walls in response to insect feeding. Based on detailed structural and kinetic analyses and molecular docking, as well as that of closely related APX enzymes, the critical residues in each substrate-binding site of PviAPX are proposed. Taken together, these observations shed new light on the function and catalysis of PviAPX and potentially benefit efforts to improve biomass conservation properties in bioenergy and forage crops.