Isoflavone reductase

The 2 -hydroxyisoflavones are reduced to the corresponding isoflavanones by a NADPH-dependent isoflavone reductase (IFR). The isoflavanones are the final isoflavonoid intermediates of pterocarpan biosynthesis. Variant IFR activities between species are thought to contribute to the stereochemistry of the pterocarpans produced, in particular, (-l-)-maackiain in P. sativum, (—)-maackiain in C. arietinum, (—)-3,9-dihydroxypterocarpan in G. max, and (—)-medicarpin in M. sativa. The (—) indicates 6aRllai stereochemistry. 

Using the crystal structures of two related RED enzymes of lignan biosynthesis, a provisional molecular model has been produced for the M. sativa IFR. A smaller binding pocket in the protein, in comparison to the other enzymes, is suggested to account for the specific enantiomer binding and processing of IFR. 

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Karamloo, F., et al.. (1999). Molecular cloning and characterization of a birch pollen minor allergen. Bet v 5, belonging to a family of isoflavone reductase-related proteins, J. Allergy Clin. Immunol., 104, 991-999. 

Min T, Kasahara H, Bedgar DL et al (2003) Crystal structures of pinoresinol-lariciresinol and phenylcoumaran benzylic ether reductases and their relationship to isoflavone reductases. J Biol Chem 278 50714-50723... 

DFR belongs to the single-domain-reductase/epimerase/dehydrogenase (RED) protein family, which has also been termed the short chain dehydrogenase/reductase (SDR) superfamily. This contains other flavonoid biosynthetic enzymes, in particular the anthocyanidin reductase (ANR), leucoanthocyanidin reductase (EAR), isoflavone reductase (IFR), and vestitone reductase (VR), as well as mammalian, bacterial, and other plant enzymes. ... 

Cooper, J.D., Qiu, F., and Paiva, N.L., Biotransformation of an exogenously supplied isoflavo-noid by transgenic tobacco cells expressing alfalfa isoflavone reductase. Plant Cell Rep., 20, 876, 2002. 

Paiva, N.L. et al., Molecular cloning of isoflavone reductase from pea (Pisum sativum L.) evidence for a 3R-isoflavanone intermediate in (+)-pisatin biosynthesis. Arch. Biochem. Biophys., 312, 501, 1994. 

Lopez-Meyer M, Paiva NL. 2002. Immunolocalization of vestitone reductase and isoflavone reductase, two enzymes involved in the biosynthesis of the phytoalexin medicarpin. Physiol Molec Plant Pathol 61 15-30. 

Oommen A, Dixon RA, Paiva NL. 1994. The elicitor-inducible alfalfa isoflavone reductase promoter confers different patterns of developmental expression in homologous and heterologous transgenic plants. Plant Cell 6 1789-1803. 

Scheme 1.1 Pathway for the biosynthesis of the major classes of flavonoids. 1, Chalcone synthase 2, chalcone isomerase 3, flavone synthase 4, flavanone 3-hydroxylase 5, flavonol synthase 6, dihydroflavonol reductase 7, anthocyanidin synthase 8, anthocyanidin glucosyltransferase 9, chalcone-ketide reductase 10, chalcone isomerase 11, isoflavone synthase 12, isoflavone 2 -hydroxylase 13, isoflavone reductase 14, pterocarpan synthase 15, pterocarpan 6a-hydroxylase 16, prenyltransferase 17, prenylcyclase.

Shoji, T., Winz, R., Iwase, T., Nakajima, K., Yamada, Y. and Hashimoto, T. (2002) Expression patterns of two tobacco isoflavone reductase-like genes and their possible roles in secondary metabolism of tobacco. Plant Mol. Biol., 50,427-AO. 

Dinkova-Kostova, A.T., Gang, D.R., Davin, L.B., Bedgar, D.L., Chu, A. and Lewis, N.G. (1996) (+)—Pinoresinol/(+)—lariciresinol reductase from Forsythia intermedia protein purification, cDNA cloning, heterologous expression and comparison to isoflavone reductase.. Biol. Chem., 46,29473-82. 

Chalcone synthase (CHS) and chalcone reductase (CHR) convert 4-coumaro-yl-CoA (15) and 3 mol malonyl-CoA (16) to trihydroxychalcone (a chalcone) (17) via tetrahydroxychalcone (a chalcone) (18). Chalcone isomerase (CHI) converts trihydroxychalcone (a chalcone) (17) into liquiritigenin (7,4/-dihydroxyllavanone, a flavanone) (19). Isoflavone synthase (IFS) converted flavanone (19) to isoflavones (20) such as daidzein (21) and genis-tein (22). Isoflavone 2/-hydroxylase (I2 H) hydroxylated isoflavones (20) to 4/-methoxyisoflavones (23). Isoflavone 2 -hydroxylase (I2 H) hydroxylated 4/-methoxyisoflavones (23) into 2/-hydroxy-4/-methoxyisoflavones (24). Isoflavone reductase (IFR) reduced 2/-hydroxy-4/-methoxyisoflavones (24) to 2/-hydroxy-4/-methoxyisoflavonones (25). Finally, vestitone reductase (VR) and 4/-methoxyisoflavanol dehydrogenase (DMID) cyclized 2/-hydroxy-4/-methoxyisoflavonones (25) to form isoflavonoids (26) such as medicarpin (27) (Fig. 4) [23,24]. 

Gang, D. R., Kasahara, H., Xia, Z. Q., Vander Mijnsbragge, K., Banw, G., Boeijan, W., Van Montagn, M., Davin, L. B., and Lewis, N. G. (1999) Evolution of plant defense mechanisms - Relationships of phenylcoumaran benzyhc ether reductases to pinores-inol-lariciresinol and isoflavone reductases. J. Biol. Chem. 274(11), 7516-7527. 

IFH, isoflavone 2 -hydroxylase IFR, isoflavone reductase PIS, pterocarpan synthase... 

Fig. 2.6 An overview of isoflavonoid biosynthesis in the Leguminosae based on recent findings. Partially characterized or uncertain steps are shown by the dotted arrows. 2HIS, 2-hydroxyisoflavanone synthase 2 OMT, 2 -0-methyltransferase (presumed) DMID, 7,2 -dihydroxy-4 -methoxyisoflavanol dehydratase HI4 OMT, hydroxyiso-flavanone 4 -0-methyltransferase I2 H, isoflavone 2 -hydroxylase IFR, isoflavone reductase PTR, pterocarpan reductase VR, vestitone reductase.

Fig. 2.7 Recent progress in the characterization of the biosynthetic pathway to (+)-pisatin in the pea, Pisum sativum. HMM, (+)-6a-hydroxymaacldain 3-0-methyltransferase IFR, isoflavone reductase SOR, sophorol reductase.

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