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12-oxophytodienoate reductase (OPRs) is an enzyme of the family of Old Yellow Enzymes (OYE). 〔 〕 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 (FMN) and catalyzses 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 escultentum'', 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. 〔 〕〔 ==Structure== 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 to 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. 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「12-oxophytodienoate reductase」の詳細全文を読む スポンサード リンク
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