Naringin inhibits the Zea mays coniferyl aldehyde dehydrogenase: an in silico and in vitro approach

Abstract

An additional reaction of the plant phenylpropanoid pathway is that catalyzed by coniferyl aldehyde dehydrogenase (HCALDH) to form cytosolic ferulic acid from coniferaldehyde. Because ferulic acid anchors lignin in cell wall polysaccharides and causes cell wall recalcitrance, the HCALDH inhibition could be a prominent target to release fermentable sugars from lignocellulose biomass and improve the saccharification efficiency. Here, we evaluated the role of the flavanone glycoside naringin (NRG), prospected in silico, as a selective inhibitor of the HCALDH of Zea mays (ZmaysHCALDH). A homotetrameric structural model in the absence of ligands was used for evaluations. The stability of the ZmaysHCALDH–NRG complex was checked via molecular dynamics simulation of the apo form (Apo–HCALDH) and that bonded to the inhibitor (NRG–HCALDH), both for the tetrameric form. The conformation bound to NRG varied less in relation to the apo form, and thus could be considered more stable. To obtain kinetic parameters, activities of a partially purified ZmaysHCALDH preparation were determined in vitro using high performance liquid chromatography. In comparison to the NRG-free control, V_max and K_m data suggested a kinetic profile of uncompetitive inhibition with respect to the substrate coniferyl aldehyde. In brief, this combinatorial in silico and in vitro approach suggest that NRG-induced inhibition of ZmaysHCALDH may be an attractive strategy to explore new clues regarding the phenylpropanoid pathway, the role of ferulic acid in the cell wall and, and mainly the digestibility of lignocellulosic biomass for biorefinery purposes.