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Title
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Crystal structure of enoyl-coenzyme A (CoA) hydratase at 2.5 angstroms resolution: a spiral fold defines the CoA-binding pocket.
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Authors
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C.K.Engel,
M.Mathieu,
J.P.Zeelen,
J.K.Hiltunen,
R.K.Wierenga.
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Ref.
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Embo J, 1996,
15,
5135-5145.
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PubMed id
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Abstract
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The crystal structure of rat liver mitochondrial enoyl-coenzyme A (CoA)
hydratase complexed with the potent inhibitor acetoacetyl-CoA has been refined
at 2.5 angstroms resolution. This enzyme catalyses the reversible addition of
water to alpha,beta-unsaturated enoyl-CoA thioesters, with nearly
diffusion-controlled reaction rates for the best substrates. Enoyl-CoA hydratase
is a hexamer of six identical subunits of 161 kDa molecular mass for the
complex. The hexamer is a dimer of trimers. The monomer is folded into a
right-handed spiral of four turns, followed by two small domains which are
involved in trimerization. Each turn of the spiral consists of two beta-strands
and an alpha-helix. The mechanism for the hydratase/dehydratase reaction follows
a syn-stereochemistry, a preference that is opposite to the nonenzymatic
reaction. The active-site architecture agrees with this stereochemistry. It
confirms the importance of Glu164 as the catalytic acid for providing the
alpha-proton during the hydratase reaction. It also shows the importance of
Glu144 as the catalytic base for the activation of a water molecule in the
hydratase reaction. The comparison of an unliganded and a liganded active site
within the same crystal form shows a water molecule in the unliganded subunit.
This water molecule is bound between the two catalytic glutamates and could
serve as the activated water during catalysis.
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