Enzyme - 3-dehydroquinate dehydratase

Alternative Name(s)

There are no alternative names for this Enzyme

Catalytic Activity

3-dehydroquinate = 3-dehydroshikimate + H2O


There are no Cofactors for this Enzyme

Reaction Mechanisms

    3-dehydroquinate dehydratase catalyses the third step in the biosynthesis of chorismate within the Shikimate pathway which synthesises aromatic compounds as well as in the degradative quinate pathway. It is a type I dehydroquinase which catalyses a cis-dehydration of the hexane ring of 3-dehydroquinate via a covalent imine intermediate (unlike the type II dehydroquinase which catalyses a trans-dehydration via an enolate intermediate). Type I dehydroquinases use a Schiff base mechanism. The pathway is essential in microorganisms and plants for the biosynthesis of compounds such as folate, ubiquinone and aromatic amino acids. The absence of this pathway in animals makes it an attractive target for antimicrobial agents.

    His143 is thought to play a part as a general acid in the formation of a Schiff base: a covalent adduct between the substrate and Lys170 of the enzyme. The role of the Schiff base is to act as an electron sink . It may also play a role in distorting the carbocyclic ring of dehydroquinate to render it more reactive. His143 is then thought to play a role in proton abstraction. Glu86 is positioned to interact with His143 and orientate it in a manner reminiscent of the serine proteases to allow it to act as a general base and abstract the C2 proton. However it is worth noting that recent research has put some doubt on this role. Any attack on the substrate from below is prevented by a beta-hairpin so only cis-elimination is possible.
    Catalytic Residues
    AA Uniprot Uniprot Resid PDB PDB Resid
    His P24670 143 1qfe 143
    Lys P24670 170 1qfe 170
    Glu P24670 86 1qfe 86
    Step Components

    overall reactant used, proton transfer, unimolecular elimination by the conjugate base, overall product formed, enzyme-substrate complex formation, bimolecular nucleophilic addition, intramolecular elimination, assisted tautomerisation (not keto-enol), intermediate formation, dehydration, schiff base formed, intermediate terminated, native state of enzyme regenerated, inferred reaction step, proton relay, intermediate collapse, enzyme-substrate complex cleavage

    Step 1.

    Glu86 deprotonates His143, which deprotonates Lys170, activating it.

    Step 2.

    Lys170 attacks the carbonyl carbon of the substrate in a nucleophilic addition.

    Step 3.

    A proton is transferred from the covalently attached lysine to the newly formed hydroxide.

    Step 4.

    Lys170 initiates an elimination of water (which obtains its proton from His143, which deprotonates Glu86) forming the Schiff base intermediate.

    Step 5.

    Glu86 deprotonates His143, which deprotonates the intermediate at the carbon adjacent to the covalently bound lysine which acts as an electron sink.

    Step 6.

    Lys170 donates its lone pair of electrons back into the ring, initiating a double bond rearrangement and elimination of water, which obtains its proton from His143, which deprotonates Glu86.

    Step 7.

    Glu86 deprotonates His143, which deprotonates water, which then attacks the carbon to which Lys170 is covalently attached.

    Step 8.

    Lys170 deprotonates the hydroxide, which causes Lys170 to be eliminated and the product to be formed.

    Step 9.

    Lys170 deprotonates His143, which deprotonates Glu86 in an inferred step that returns the enzyme to its starting state.


    The products of the reaction.

Reaction Parameters

There are no kinetic parameters information for this Enzyme

Associated Proteins

Protein name Organism
Catabolic 3-dehydroquinase Emericella nidulans (strain FGSC A4 / ATCC 38163 / CBS 112.46 / NRRL 194 / M139)
3-dehydroquinate dehydratase 2 Pseudomonas putida (strain ATCC 47054 / DSM 6125 / NCIMB 11950 / KT2440)
3-dehydroquinate dehydratase 1 Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1)
Catabolic 3-dehydroquinase 2 Neosartorya fischeri (strain ATCC 1020 / DSM 3700 / CBS 544.65 / FGSC A1164 / JCM 1740 / NRRL 181 / WB 181)
3-dehydroquinate dehydratase Escherichia coli (strain K12)