Biology:12-oxophytodienoate reductase

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Short description: Class of enzymes
Structure of 12-oxophytodienoate reductase (OPR3) bound to FMN cofactor, created in Pymol.[1]
12-oxophytodienoate reductase
Identifiers
EC number1.3.1.42
CAS number101150-03-2
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

12-oxophytodienoate reductase (OPRs) is an enzyme of the family of Old Yellow Enzymes (OYE).[2] 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.[3] The OPR enzyme utilizes the cofactor flavin mononucleotide (FMN) and catalyzes the following reaction in the jasmonic acid synthesis pathway:[4]

Reaction catalyzed by 12-oxophytodienoate reductase in the jasmonic acid synthesis pathway.[1]

This reaction occurs in peroxisomes in plants.[5] Several isozymes have been discovered, with varying substrate stereospecificity: three in Solanum lycopersicum, 13 in Oryza sativa, and five in Arabidopsis thaliana.[6] 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.[7][4]

Structure

12-oxophytodienoate reductase structure resembles OYE enzymes and has been elucidated by x-ray crystal structures.[1] The cDNA encodes 372 amino acids for this enzyme.[2] It exhibits a barrel fold of eight parallel beta-strands surrounded by eight alpha-helices to create a barrel shape.[6] 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.[6] 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.[6]

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.[1] The residues Tyr78 and Tyr246 that are at the mouth of the active site are responsible for the higher enantioselectivity of OPR1.[8][1] 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.[8][1]

12-oxophytodienoate reductase isomers OPR3 (blue) and OPR1 (green) with FMN cofactor (pink).[1]

12-oxophytodienoate reductase has also been shown to practice self-inhibition by dimerization.[6] This is the only flavoprotein known to dimerize for inhibition and this dimerization is thought to be regulated by phosphorylation.[6] The dimerization occurs by the mutual binding of two loops into the two active sites.[6] These loops are highly evolutionarily conserved, indicating the dimerization is purposeful and significant in regulation.[6]

12-oxophytodienoate reductase (OPR3) dimerized to itself. This dimer provides self-inhibition of the enzyme.[1]

Mechanism

The reduction mechanism employed has been shown to be a ping-pong, bi-bi mechanism.[6] The FMN cofactor is first reduced by NADPH, the substrate is then bound, and finally the substrate is reduced by a hydride transfer from NADPH to the substrate’s beta carbon.[6] The Km of OPR3 in Zea mays was found to be 190 micromolar for its substrate OPDA.[9]

Biological Function

The reaction catalyzed by 12-oxophytodienoate reductase is in the jasmonic acid biosynthesis pathway. Jasmonic acid is known for its importance as a gene regulator for development and defense.[4][10][11][12]

OPR3 is shown to be induced by touch, wind, UV light, application of detergent, wounding, and brassinosteroids.[4] In wound response, its activity has been shown to partially depend on jasmonic acid perception.[4] It is also shown to have greater enzyme efficiency than OPR1 and OPR2 in Arabidopsis thaliana, showing it is the significant enzyme in the jasmonic acid biosynthesis pathway.[4]

Relevance to Agriculture

This enzyme is of interest in plant biology research because the disrupted OPR3 gene has been shown to cause male sterility in Arabidopsis thaliana.[13] This is a point of interest in understanding the factors surrounding viable pollen development, a focus of research in the agriculture industry.[13]

Relevance to Phytoremediation

OPR has shown to also function in the reduction of explosive 2,4,6-trinitrotoluene (TNT).[14] Because TNT is a known toxic, environmental pollutant that is difficult to degrade, the use of phytoremediation to clean up sites contaminated with TNT is of significant interest.[14] OPR1 degraded TNT faster and with greater amount of degraded products than other isozymes.[14] This enzyme could therefore be used in phytoremediation.[14]

Phylogenetics

A phylogenetic analysis studying the structural evolution and functional divergence of the various OPR paralogues found seven conserved sub-families and suggested expansion of the OPR families occurred in land plants.[15] A total of 74 OPR genes in 11 species from six major plant lineages were found.[15] Surprisingly, introns were found to differ in length and number, but conserved in position, indicating successive intron loss.[15] The study also indicated that the substrate binding loop and the alpha-helices, but not the beta-sheets, were critical for functional divergence after sub-families were established and are therefore important in the OPR proteins.[15]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 "X-ray structure of 12-oxophytodienoate reductase 1 provides structural insight into substrate binding and specificity within the family of OYE.". Structure 9 (5): 419–29. 2001. doi:10.1016/s0969-2126(01)00602-5. PMID 11377202. 
  2. ↑ 2.0 2.1 "Molecular cloning and characterization of 12-oxophytodienoate reductase, an enzyme of the octadecanoid signaling pathway from Arabidopsis thaliana. Structural and functional relationship to yeast old yellow enzyme.". J Biol Chem 272 (44): 28066–72. 1997. doi:10.1074/jbc.272.44.28066. PMID 9346960. 
  3. ↑ "Wheat oxophytodienoate reductase gene TaOPR1 confers salinity tolerance via enhancement of abscisic acid signaling and reactive oxygen species scavenging.". Plant Physiol 161 (3): 1217–28. 2013. doi:10.1104/pp.112.211854. PMID 23321418. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 "12-Oxophytodienoate reductase 3 (OPR3) is the isoenzyme involved in jasmonate biosynthesis.". Planta 210 (6): 979–84. 2000. doi:10.1007/s004250050706. PMID 10872231. 
  5. ↑ "Characterization and cDNA-microarray expression analysis of 12-oxophytodienoate reductases reveals differential roles for octadecanoid biosynthesis in the local versus the systemic wound response.". Plant J 32 (4): 585–601. 2002. doi:10.1046/j.1365-313x.2002.01449.x. PMID 12445129. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 "Crystal structure of 12-oxophytodienoate reductase 3 from tomato: self-inhibition by dimerization.". Proc Natl Acad Sci U S A 103 (39): 14337–42. 2006. doi:10.1073/pnas.0606603103. PMID 16983071. Bibcode: 2006PNAS..10314337B. 
  7. ↑ "12-Oxophytodienoate-10,11-reductase: occurrence of two isoenzymes of different specificity against stereoisomers of 12-oxophytodienoic acid". Plant Physiol 118 (4): 1345–51. 1998. doi:10.1104/pp.118.4.1345. PMID 9847108. 
  8. ↑ 8.0 8.1 "Structural basis of substrate specificity of plant 12-oxophytodienoate reductases.". J Mol Biol 392 (5): 1266–77. 2009. doi:10.1016/j.jmb.2009.07.087. PMID 19660473. 
  9. ↑ "Characterization of 12-oxo-phytodienoic Acid reductase in corn: the jasmonic Acid pathway.". Plant Physiol 80 (1): 202–5. 1986. doi:10.1104/pp.80.1.202. PMID 16664582. 
  10. ↑ "Insect elicitors and exposure to green leafy volatiles differentially upregulate major octadecanoids and transcripts of 12-oxo phytodienoic acid reductases in Zea mays.". Mol Plant Microbe Interact 20 (6): 707–16. 2007. doi:10.1094/MPMI-20-6-0707. PMID 17555278. 
  11. ↑ "An Arabidopsis gene induced by wounding functionally homologous to flavoprotein oxidoreductases.". Plant Mol Biol 44 (1): 61–71. 2000. doi:10.1023/A:1006464822434. PMID 11094980. 
  12. ↑ "Identification of the OsOPR7 gene encoding 12-oxophytodienoate reductase involved in the biosynthesis of jasmonic acid in rice.". Planta 227 (3): 517–26. 2008. doi:10.1007/s00425-007-0635-7. PMID 17938955. 
  13. ↑ 13.0 13.1 "The Arabidopsis male-sterile mutant, opr3, lacks the 12-oxophytodienoic acid reductase required for jasmonate synthesis.". Proc Natl Acad Sci U S A 97 (19): 10625–30. 2000. doi:10.1073/pnas.190264497. PMID 10973494. Bibcode: 2000PNAS...9710625S. 
  14. ↑ 14.0 14.1 14.2 14.3 "The role of oxophytodienoate reductases in the detoxification of the explosive 2,4,6-trinitrotoluene by Arabidopsis.". Plant Physiol 151 (1): 253–61. 2009. doi:10.1104/pp.109.141598. PMID 19605548. 
  15. ↑ 15.0 15.1 15.2 15.3 "Phylogenetic analysis, structural evolution and functional divergence of the 12-oxo-phytodienoate acid reductase gene family in plants.". BMC Evol Biol 9: 90. 2009. doi:10.1186/1471-2148-9-90. PMID 19416520. 



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