Journal
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Volume 24, Issue 2, Pages -Publisher
MDPI
DOI: 10.3390/ijms24021778
Keywords
ascorbate; switchgrass; ROS; stress; phenylpropanoids; ascorbate peroxidase; lignification; X-ray crystallography; oxidation
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PviAPX is a key antioxidant enzyme that scavenges H2O2 in plants. It can oxidize a broad range of phenylpropanoids, contributing to the strengthening of cell walls. These findings provide new insights into the function and catalysis of PviAPX and have potential implications for improving plant health and biomass quality in bioenergy and forage crops.
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 a bound ascorbate molecule at the gamma-heme edge pocket as in other APXs. Our results indicated that the H2O2-dependent oxidation of ascorbate displayed positive cooperativity. Significantly, our study suggested that PviAPX can oxidize a broad range of phenylpropanoids with delta-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 improve plant health and biomass quality in bioenergy and forage crops.
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