Publications

• Crystal structure and catalytic mechanism of leucoanthocyanidin reductase from Vitis vinifera.

  Mauge C., Granier T., d'Estaintot B.L., Gargouri M., Manigand C., Schmitter J.M., Chaudiere J., Gallois B.

  Leucoanthocyanidin reductase (LAR) catalyzes the NADPH-dependent reduction of 2R,3S,4S-flavan-3,4-diols into 2R,3S-flavan-3-ols, a subfamily of flavonoids that is important for plant survival and for human nutrition. LAR1 from Vitis vinifera has been co-crystallized with or without NADPH and one o ... >> More

  Leucoanthocyanidin reductase (LAR) catalyzes the NADPH-dependent reduction of 2R,3S,4S-flavan-3,4-diols into 2R,3S-flavan-3-ols, a subfamily of flavonoids that is important for plant survival and for human nutrition. LAR1 from Vitis vinifera has been co-crystallized with or without NADPH and one of its natural products, (+)-catechin. Crystals diffract to a resolution between 1.75 and 2.72 A. The coenzyme and substrate binding pocket is preformed in the apoprotein and not markedly altered upon NADPH binding. The structure of the abortive ternary complex, determined at a resolution of 2.28 A, indicates the ordering of a short 3(10) helix associated with substrate binding and suggests that His122 and Lys140 act as acid-base catalysts. Based on our 3D structures, a two-step catalytic mechanism is proposed, in which a concerted dehydration precedes an NADPH-mediated hydride transfer at C4. The dehydration step involves a Lys-catalyzed deprotonation of the phenolic OH7 through a bridging water molecule and a His-catalyzed protonation of the benzylic hydroxyl at C4. The resulting quinone methide serves as an electrophilic target for hydride transfer at C4. LAR belongs to the short-chain dehydrogenase/reductase superfamily and to the PIP (pinoresinol-lariciresinol reductase, isoflavone reductase, and phenylcoumaran benzylic ether reductase) family. Our data support the concept that all PIP enzymes reduce a quinone methide intermediate and that the major role of the only residue that has been conserved from the short-chain dehydrogenase/reductase catalytic triad (Ser...TyrXXXLys), that is, lysine, is to promote the formation of this intermediate by catalyzing the deprotonation of a phenolic hydroxyl. For some PIP enzymes, this lysine-catalyzed proton abstraction may be sufficient to trigger the extrusion of the leaving group, whereas in LAR, the extrusion of a hydroxide group requires a more sophisticated mechanism of concerted acid-base catalysis that involves histidine and takes advantage of the OH4, OH5, and OH7 substituents of leucoanthocyanidins. << Less

  J Mol Biol 397:1079-1091(2010) [PubMed] [EuropePMC]

• Synthesis of 3,4-cis-[3H]leucocyanidin and enzymatic reduction to catechin.

  Tanner G.J., Kristiansen K.N.

  A novel method is presented for the synthesis and purification of (+)-2,3-trans-3,4-cis-[4-3H]leucocyanidin. Soluble enzyme extracts from developing barley grains and leaves of the forage legume Onobrychis viciifolia (sainfoin) catalyzed the NAD(P)H-dependent reduction of (+)-2,3-trans-3,4-cis-[4- ... >> More

  A novel method is presented for the synthesis and purification of (+)-2,3-trans-3,4-cis-[4-3H]leucocyanidin. Soluble enzyme extracts from developing barley grains and leaves of the forage legume Onobrychis viciifolia (sainfoin) catalyzed the NAD(P)H-dependent reduction of (+)-2,3-trans-3,4-cis-[4-3H]leucocyanidin to (+)-[4-3H]catechin. NADPH was the preferred substrate. With extracts of barley the rate of reaction with 1 mM NADH was 20% of the rate found with NADPH. With extracts from both tissues there was a broad pH optimum around pH 6.6. << Less

  Anal Biochem 209:274-277(1993) [PubMed] [EuropePMC]

• Proanthocyanidin biosynthesis in plants. Purification of legume leucoanthocyanidin reductase and molecular cloning of its cDNA.

  Tanner G.J., Francki K.T., Abrahams S., Watson J.M., Larkin P.J., Ashton A.R.

  Leucoanthocyanidin reductase (LAR) catalyzes the synthesis of catechin, an initiating monomer of condensed tannin or proanthocyanidin (PA) synthesis, from 3,4-cis-leucocyanidin and thus is the first committed step in PA biosynthesis. The enzyme was purified to near homogeneity from PA-rich leaves ... >> More

  Leucoanthocyanidin reductase (LAR) catalyzes the synthesis of catechin, an initiating monomer of condensed tannin or proanthocyanidin (PA) synthesis, from 3,4-cis-leucocyanidin and thus is the first committed step in PA biosynthesis. The enzyme was purified to near homogeneity from PA-rich leaves of the legume Desmodium uncinatum (Jacq.) DC, partially sequenced and the corresponding cDNA cloned. The identity of the enzyme was confirmed by expressing active recombinant LAR in Escherichia coli and in tobacco and white clover. The enzyme is a monomer of 43 kDa (382 amino acids) and is most active synthesizing catechin (specific activity of approximately 10 micromol min+1 mg of protein+1) but also synthesizes afzelechin and gallocatechin. LAR is most closely related to the isoflavone reductase group of plant enzymes that are part of the Reductase-Epimerase-Dehydrogenase (RED) family of proteins. Unlike all other plant isoflavone reductase homologues that are about 320 amino acids long, LAR has an additional 65-amino acid C-terminal extension whose function is not known. Curiously, although Arabidopsis makes PA, there is no obvious LAR orthologue in the Arabidopsis genome. This may be because Arabidopsis seems to produce only an epicatechin, rather than a dual catechin/epicatechin-based PA similar to many other plants. << Less

  J. Biol. Chem. 278:31647-31656(2003) [PubMed] [EuropePMC]