1ey3
From Proteopedia
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STRUCTURE OF ENOYL-COA HYDRATASE COMPLEXED WITH THE SUBSTRATE DAC-COA
Overview
We have determined the crystal structure of the enzyme enoyl-CoA hydratase, (ECH) from rat liver with the bound substrate, 4-(N,N-dimethylamino)cinnamoyl-CoA using X-ray diffraction data to a, resolution of 2.3 A. In addition to the thiolester substrate, the, catalytic water, which is added in the hydration reaction, has been, modeled into well-defined electron density in each of the six active sites, of the physiological hexamer within the crystallographic asymmetric unit., The catalytic water bridges Glu(144) and Glu(164) of the enzyme and has a, lone pair of electrons poised to react with C(3) of the enzyme-bound, alpha,beta-unsaturated thiolester. The water molecule, which bridges two, glutamate residues, is reminiscent of the enolase active site. However, unlike enolase, which has a lysine available to donate a proton, there are, no other sources of protons available from other active site residues in, ECH. Furthermore, an analysis of the hydrogen-bonding network of the, active site suggests that both Glu(144) and Glu(164) are ionized and carry, a negative charge with no reasonable place to have a protonated, carboxylate. This lack of hydrogen-bonding acceptors that could, accommodate a source of a proton, other than from the water molecule, leads to a hypothesis that the three atoms from a single water molecule, are added across the double bond to form the hydrated product. The, structural results are discussed in connection with details of the, mechanism, which have been elucidated from kinetics, site-directed, mutagenesis, and spectroscopy of enzyme-substrate species, in presenting, an atomic-resolution mechanism of the reaction. Contrary to the previous, interpretation, the structure of the E-S complex together with previously, determined kinetic isotope effects is consistent with either a concerted, mechanism or an E1cb stepwise mechanism.
About this Structure
1EY3 is a Single protein structure of sequence from Rattus norvegicus with DAK as ligand. Active as Enoyl-CoA hydratase, with EC number 4.2.1.17 Full crystallographic information is available from OCA.
Reference
Structural mechanism of enoyl-CoA hydratase: three atoms from a single water are added in either an E1cb stepwise or concerted fashion., Bahnson BJ, Anderson VE, Petsko GA, Biochemistry. 2002 Feb 26;41(8):2621-9. PMID:11851409
Page seeded by OCA on Tue Nov 20 14:25:00 2007
