page_title: 12-oxophytodienoate reductase
section_title: Structure
hierarchical_section_title: 12-oxophytodienoate reductase / Structure
caption_attribution_description: English: 12-oxophytodienoate reductase isomers OPR3 (blue) and OPR1 (green) with FMN cofactor (pink).
context_page_description: 12-oxophytodienoate reductase is an enzyme of the family of Old Yellow Enzymes. OPRs are grouped into two groups: OPRI and OPRII – the second group is the focus of this article, as the function of the first group is unknown, but is the subject of current research. The OPR enzyme utilizes the cofactor flavin mononucleotide and catalyzes the following reaction in the jasmonic acid synthesis pathway:
  This reaction occurs in peroxisomes in plants. Several isozymes have been discovered, with varying substrate stereospecificity: three in Lycopersicon esculentum, 13 in Oryza sativa, and five in Arabidopsis thaliana. The OPR3 isozyme is most extensively studied because it can reduce all 4 stereoisomers of the substrate, OPDA and because it has shown to be the most significant enzyme in the jasmonic acid synthesis pathway.
context_section_description: 12-oxophytodienoate reductase structure resembles OYE enzymes and has been elucidated by x-ray crystal structures. The cDNA encodes 372 amino acids for this enzyme. It exhibits a barrel fold of eight parallel beta-strands surrounded by eight alpha-helices to create a barrel shape. Turns at the N-terminus loops of the beta-strands have been shown to contain three to four amino acid residues and the C-terminus loops range between three and 47 amino acid residues. The C-terminus loops largely make up the active site and the larger range of the amount of residues is due to the diversity in the different isozyme active sites.
  OPR3, the most extensively studied isoform of 12-oxophytodienoate reductase, has a wider binding pocket than OPR1, which is enantioselective for only one OPDA substrate enantiomer. The residues Tyr78 and Tyr246 that are at the mouth of the active site are responsible for the higher enantioselectivity of OPR1. OPR1 and OPR3 have identical substrate binding residues, but the difference in the width of the mouth of the active site determines the OPR1 specificity.
  12-oxophytodienoate reductase has also been shown to practice self-inhibition by dimerization. This is the only flavoprotein known to dimerize for inhibition and this dimerization is thought to be regulated by phosphorylation. The dimerization occurs by the mutual binding of two loops into the two active sites. These loops are highly evolutionarily conserved, indicating the dimerization is purposeful and significant in regulation.
caption: 12-oxophytodienoate reductase isomers OPR3 (blue) and OPR1 (green) with FMN cofactor (pink).[1]
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