2QYS

Structure of Eugenol Synthase from Ocimum basilicum

Summary for 2QYS

• Entry DOI: 10.2210/pdb2qys/pdb
• Related: 2QW8 2QX7 2QZ2 2R2G
• Descriptor: Eugenol synthase 1 (2 entities in total)
• Functional Keywords: eugenol, phenylpropene, pip reductase, short-chain dehydrogenase/reductase, plant protein
• Biological source: Ocimum basilicum (sweet basil)
• Total number of polymer chains: 2
• Total formula weight: 71978.93

Authors

Louie, G.V.,Noel, J.P.,Bowman, M.E. (deposition date: 2007-08-15, release date: 2008-01-15, Last modification date: 2023-08-30)

Primary citation

Louie, G.V.,Baiga, T.J.,Bowman, M.E.,Koeduka, T.,Taylor, J.H.,Spassova, S.M.,Pichersky, E.,Noel, J.P.
Structure and reaction mechanism of basil eugenol synthase
Plos One, 2:e993-e993, 2007

PubMed Abstract: Phenylpropenes, a large group of plant volatile compounds that serve in multiple roles in defense and pollinator attraction, contain a propenyl side chain. Eugenol synthase (EGS) catalyzes the reductive displacement of acetate from the propenyl side chain of the substrate coniferyl acetate to produce the allyl-phenylpropene eugenol. We report here the structure determination of EGS from basil (Ocimum basilicum) by protein x-ray crystallography. EGS is structurally related to the short-chain dehydrogenase/reductases (SDRs), and in particular, enzymes in the isoflavone-reductase-like subfamily. The structure of a ternary complex of EGS bound to the cofactor NADP(H) and a mixed competitive inhibitor EMDF ((7S,8S)-ethyl (7,8-methylene)-dihydroferulate) provides a detailed view of the binding interactions within the EGS active site and a starting point for mutagenic examination of the unusual reductive mechanism of EGS. The key interactions between EMDF and the EGS-holoenzyme include stacking of the phenyl ring of EMDF against the cofactor's nicotinamide ring and a water-mediated hydrogen-bonding interaction between the EMDF 4-hydroxy group and the side-chain amino moiety of a conserved lysine residue, Lys132. The C4 carbon of nicotinamide resides immediately adjacent to the site of hydride addition, the C7 carbon of cinnamyl acetate substrates. The inhibitor-bound EGS structure suggests a two-step reaction mechanism involving the formation of a quinone-methide prior to reduction. The formation of this intermediate is promoted by a hydrogen-bonding network that favors deprotonation of the substrate's 4-hydroxyl group and disfavors binding of the acetate moiety, akin to a push-pull catalytic mechanism. Notably, the catalytic involvement in EGS of the conserved Lys132 in preparing the phenolic substrate for quinone methide formation through the proton-relay network appears to be an adaptation of the analogous role in hydrogen bonding played by the equivalent lysine residue in other enzymes of the SDR family.

PubMed: 17912370
DOI: 10.1371/journal.pone.0000993

Experimental method

X-RAY DIFFRACTION (1.8 Å)