Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.1.6 (CAD)
 4,420 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cinnamyl alcohol dehydrogenase (CAD; EC 1.1.195) catalyses the conversion of p-hydroxy-cinnamaldehydes to the corresponding alcohols and is considered a key enzyme in lignin biosynthesis. In a previous study, an atypical form of CAD (CAD 1) was identified in Eucalyptus gunnii [12]. We report here the molecular cloning and characterization of the corresponding cDNA, CAD 1-5, which encodes this novel aromatic alcohol dehydrogenase. The identity of CAD 1-5 was unambiguously confirmed by sequence comparison of the cDNA with peptide sequences derived from purified CAD 1 protein and by functional expression of CAD 1 recombinant protein in Escherichia coli. Both native and recombinant CAD 1 exhibit high affinity towards lignin precursors including 4-coumaraldehyde and coniferaldehyde, but they do not accept sinapaldehyde. Moreover, recombinant CAD 1 can also utilize a wide range of aromatic substrates including unsubstituted and substituted benzaldehydes. The open reading frame of CAD 1-5 encodes a protein with a calculated molecular mass of 35,790 Da and an isoelectric point of 8.1. Although sequence comparisons with proteins in databases revealed significant similarities with dihydroflavonol-4-reductases (DFR; EC 1.1.1.219) from a wide range of plant species, the most striking similarity was found with cinnamoyl-CoA reductase (CCR; EC 1.2.1.44), the enzyme which directly precedes CAD in the lignin biosynthetic pathway. RNA blot analysis and immunolocalization experiments indicated that CAD 1 is expressed in both lignified and unlignified tissues/cells. Based on the catalytic activity of CAD 1 in vitro and its localization in planta, CAD 1 may function as an 'alternative' enzyme in the lignin biosynthetic pathway. However, additional roles in phenolic metabolism are not excluded.
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PMID:A novel aromatic alcohol dehydrogenase in higher plants: molecular cloning and expression. 952 8

Homologous antisense constructs were used to down-regulate tobacco cinnamyl-alcohol dehydrogenase (CAD; EC 1.1.1.195) and cinnamoyl-CoA reductase (CCR; EC 1.2.1.44) activities in the lignin monomer biosynthetic pathway. CCR converts activated cinnamic acids (hydroxycinnamoyl-SCoAs) to cinnamaldehydes; cinnamaldehydes are then reduced to cinnamyl alcohols by CAD. The transformations caused the incorporation of nontraditional components into the extractable tobacco lignins, as evidenced by NMR. Isolated lignin of antisense-CAD tobacco contained fewer coniferyl and sinapyl alcohol-derived units that were compensated for by elevated levels of benzaldehydes and cinnamaldehydes. Products from radical coupling of cinnamaldehydes, particularly sinapaldehyde, which were barely discernible in normal tobacco, were major components of the antisense-CAD tobacco lignin. Lignin content was reduced in antisense-CCR tobacco, which displayed a markedly reduced vigor. That lignin contained fewer coniferyl alcohol-derived units and significant levels of tyramine ferulate. Tyramine ferulate is a sink for the anticipated build-up of feruloyl-SCoA, and may be up-regulated in response to a deficit of coniferyl alcohol. Although it is not yet clear whether the modified lignins are true structural components of the cell wall, the findings provide further indications of the metabolic plasticity of plant lignification. An ability to produce lignin from alternative monomers would open new avenues for manipulation of lignin by genetic biotechnologies.
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PMID:NMR characterization of altered lignins extracted from tobacco plants down-regulated for lignification enzymes cinnamylalcohol dehydrogenase and cinnamoyl-CoA reductase. 978 81

Transgenic plants severely suppressed in the activity of cinnamoyl-CoA reductase were produced by introduction of a partial sense CCR transgene into tobacco. Five transgenic lines with CCR activities ranging from 2 to 48% of wild-type values were selected for further study. Some lines showed a range of aberrant phenotypes including reduced growth, and all had changes to lignin structure making the polymer more susceptible to alkali extraction. The most severely CCR-suppressed line also had significantly decreased lignin content and an increased proportion of free phenolic groups in non-condensed lignin. These changes are likely to make the lignin easier to extract during chemical pulping. Direct Kraft pulping trials confirmed this. More lignin could be removed from the transgenic wood than from wild-type wood at the same alkali charge. A similar improvement in pulping efficiency was recently shown for poplar trees expressing an antisense cinnamyl alcohol dehydrogenase gene. Pulping experiments performed here on CAD-antisense tobacco plants produced near-identical results--the modified lignin was more easily removed during pulping without any adverse effects on the quality of the pulp or paper produced. These results suggest that pulping experiments performed in tobacco can be predictive of the results that will be obtained in trees such as poplar, extending the utility of the tobacco model. On the basis of our results on CCR manipulation in tobacco, we predict that CCR-suppressed trees may show pulping benefits. However, it is likely that CCR-suppression will not be the optimal target for genetic manipulation of pulping character due to the potential associated growth defects.
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PMID:Improved paper pulp from plants with suppressed cinnamoyl-CoA reductase or cinnamyl alcohol dehydrogenase. 1243 80

Lignin and lignans share monolignols as common precursors and are both potentially involved in plant defence against pathogens. In this study, we investigated the effects of fungal elicitors on lignin and lignan metabolism in flax (Linum usitatissimum) cell suspensions. Cell suspension cultures of flax were treated with elicitor preparations made from mycelium extracts of Botrytis cinerea, Phoma exigua and Fusarium oxysporum F ssp lini. Elicitors induced a rapid stimulation of the monolignol pathway, as confirmed by the increase in PAL (phenylalanine ammonia-lyase, EC 4.1.3.5), CCR (cinnamoyl-CoA reductase EC 1.2.1.44) and CAD (cinnamyl alcohol dehydrogenase EC 1.1.1.195) gene expression and PAL activity. At the same time, CCR activity only increased significantly in F. oxysporum-treated cells 24 h post elicitation. On the other hand, CAD activity measured for coniferyl alcohol formation was transiently decreased but a substrate-specific activation of CAD activity was observed in F. oxysporum-treated cells when using sinapyl alcohol as substrate. The accumulation of monolignol-derived products varied according to the elicitor used. B. cinerea or P. exigua-elicited cell cultures were characterised by a reinforcement of the cell wall by a deposit of 8-O-4'-linked non-condensed lignin structures and phenolic monomers, while at the same time no stimulation of 8-8'-linked lignan or 8-5'-linked phenylcoumaran lignan accumulation was observed. Additionally, elicitation of cell cultures with F. oxysporum extracts even triggered a strong incorporation of monolignols in the non condensed labile ether-linked lignin fraction concomitantly with a decrease in lignan and phenylcoumaran lignan accumulation. Several hypotheses are proposed to explain the putative role of these compounds in the defence response of flax cells against pathogens.
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PMID:Differential accumulation of monolignol-derived compounds in elicited flax (Linum usitatissimum) cell suspension cultures. 1629 60