Inhibition of cinnamyl-alcohol-dehydrogenase activity and lignin synthesis in poplar (Populus x euramericana Dode) tissues by two organic compounds

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Abstract
Two organic compounds, N-(O-hydroxyphenul)-and N-(O-aminophenyl)sulfinamoyltertiobutyl acetate (OHPAS and NH2PAS, respectively) have been designed for inhibiting cinnamylalcohol dehydrogenase (EC 1.1.1.2), a zinc metalloenzyme involved specifically in lignification. This paper describes their effects in vitro on the activity of the enzyme isolated from poplar and in vivo on the lignification of poplar tissues. The enzyme inhibition was time- and dose-dependent and pseudoirreversible indicating that these compounds could act as suicide inhibitors. Neither OHPAS nor NH2PAS exhibited affinity towards other plant zinc metalloenzymes or phenolic enzymes tested. Only NH2PAS exerted an effect on cinnamoyl: CoA reductase, another specific enzyme of lignification. In addition, these inhibitors, at the concentration of 80 μM, reduced the fluxes of lignin synthesis in poplar stems by 45%. These results show that OHPAS and NH2PAS could become useful tools for reducing lignification in plants.