1j00
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E. coli Thioesterase I/Protease I/Lysophospholipase L1 in complexed with diethyl phosphono moiety
OverviewOverview
Escherichia coli thioesterase I (TAP) is a multifunctional enzyme, possessing activities of thioesterase, esterase, arylesterase, protease, and lysophospholipase. In particular, TAP has stereoselectivity for amino, acid derivative substrates, hence it is useful for the kinetic resolution, of racemic mixtures of industrial chemicals. In the present work, the, crystal structure of native TAP was determined at 1.9A, revealing a, minimal SGNH-hydrolase fold. The structure of TAP in complex with a, diethyl phosphono moiety (DEP) identified its catalytic triad, Ser10-Asp154-His157, and oxyanion hole, Ser10-Gly44-Asn73. The oxyanion, hole of TAP consists of three residues each separated from the other by, more than 3.5A, implying that all of them are highly polarized when, substrate bound. The catalytic (His)C(epsilon1)-H...O=C hydrogen bond, usually plays a role in the catalytic mechanisms of most serine, hydrolases, however, there were none present in SGNH-hydrolases. We, propose that the existence of the highly polarized tri-residue-constituted, oxyanion hole compensates for the lack of a (His)C(epsilon1)-H...O=C, hydrogen bond. This suggests that members of the SGNH-hydrolase family may, employ a unique catalytic mechanism. In addition, most SGNH-hydrolases, have low sequence identities and presently there is no clear criterion to, define consensus sequence blocks. Through comparison of TAP and the three, SGNH-hydrolase structures currently known, we have identified a unique, hydrogen bond network which stabilizes the catalytic center: a newly, discovered structural feature of SGNH-hydrolases. We have defined these, consensus sequence blocks providing a basis for the sub-classification of, SGNH-hydrolases.
About this StructureAbout this Structure
1J00 is a Single protein structure of sequence from Escherichia coli with SO4 as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of Escherichia coli thioesterase I/protease I/lysophospholipase L1: consensus sequence blocks constitute the catalytic center of SGNH-hydrolases through a conserved hydrogen bond network., Lo YC, Lin SC, Shaw JF, Liaw YC, J Mol Biol. 2003 Jul 11;330(3):539-51. PMID:12842470
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