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Evolution of Plant Defense Mechanisms

1999; Elsevier BV; Volume: 274; Issue: 11 Linguagem: Inglês

10.1074/jbc.274.11.7516

1083-351X

David R. Gang, Hiroyuki Kasahara, Zhiqiang Xia, Kristine Vander Mijnsbrugge, Guy Bauw, Wout Boerjan, Marc Van Montagu, Laurence Davin, Norman Lewis,

Bioactive natural compounds

Pinoresinol-lariciresinol and isoflavone reductase classes are phylogenetically related, as is a third, the so-called "isoflavone reductase homologs." This study establishes the first known catalytic function for the latter, as being able to engender the NADPH-dependent reduction of phenylcoumaran benzylic ethers. Accordingly, all three reductase classes are involved in the biosynthesis of important and related phenylpropanoid-derived plant defense compounds. In this investigation, the phenylcoumaran benzylic ether reductase from the gymnosperm, Pinus taeda , was cloned, with the recombinant protein heterologously expressed in Escherichia coli . The purified enzyme reduces the benzylic ether functionalities of both dehydrodiconiferyl alcohol and dihydrodehydrodiconiferyl alcohol, with a higher affinity for the former, as measured by apparent K m and V max values and observed kinetic 3 H-isotope effects. It abstracts the 4 R -hydride of the required NADPH cofactor in a manner analogous to that of the pinoresinol-lariciresinol reductases and isoflavone reductases. A similar catalytic function was observed for the corresponding recombinant reductase whose gene was cloned from the angiosperm, Populus trichocarpa . Interestingly, both pinoresinol-lariciresinol reductases and isoflavone reductases catalyze enantiospecific conversions, whereas the phenylcoumaran benzylic ether reductase only shows regiospecific discrimination. A possible evolutionary relationship among the three reductase classes is proposed, based on the supposition that phenylcoumaran benzylic ether reductases represent the progenitors of pinoresinol-lariciresinol and isoflavone reductases.