Document Detail


Assessing the roles of essential functional groups in the mechanism of homoserine succinyltransferase.
MedLine Citation:
PMID:  17442255     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Homoserine acyltransferases catalyze the commitment step to methionine and other important biological precursors which make this class of enzymes essential for the survival of bacteria, plants and fungi. This class of enzymes is not found in humans, making them an attractive new target for antimicrobial design. Homoserine O-succinyltransferase (HST) is a representative from this class, with little known about the key amino acids involved in substrate specificity and catalysis. HST from Escherichia coli has been cloned, purified and kinetically characterized. Through site-directed mutagenesis and steady-state kinetic studies the residues that comprise a catalytic triad for HST, the catalytic cysteine nucleophile, an active site acid-base histidine, and the base orienting glutamate, have been identified and characterized. Several residues which confer substrate specificity for both homoserine and succinyl-CoA have also been identified and kinetically evaluated. Mutations of an active site glutamate to either aspartate or alanine drastically increase the K(m) for homoserine, assigning this glutamate to a binding role for the alpha-amino group of homoserine. An active site arginine orients the carboxyl moiety of homoserine, while the carboxyl moiety of succinyl-CoA is positioned for catalysis by a lysine residue. Removing functionality at either of these positions alters the enzyme's ability to effectively utilize homoserine or succinyl-CoA, respectively, reflected in an increased K(m) and decreased catalytic efficiency. The data presented here provides new details of the catalytic mechanism of succinyltransferases, resolves a controversy between alternative mechanistic hypotheses, and provides a starting point for the development of selective inhibitors of HST.
Authors:
David M Coe; Ronald E Viola
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Publication Detail:
Type:  Journal Article     Date:  2007-04-02
Journal Detail:
Title:  Archives of biochemistry and biophysics     Volume:  461     ISSN:  0003-9861     ISO Abbreviation:  Arch. Biochem. Biophys.     Publication Date:  2007 May 
Date Detail:
Created Date:  2007-05-08     Completed Date:  2007-06-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0372430     Medline TA:  Arch Biochem Biophys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  211-8     Citation Subset:  IM    
Affiliation:
Department of Chemistry, University of Toledo, 2801 W. Bancroft Street, Toledo, OH 43606, USA.
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MeSH Terms
Descriptor/Qualifier:
Amino Acid Sequence
Amino Acids / chemistry*,  genetics,  physiology*
Binding Sites
Catalysis
Catalytic Domain
Escherichia coli Proteins / chemistry*,  genetics,  physiology*
Homoserine / metabolism
Homoserine O-Succinyltransferase / chemistry*,  genetics,  physiology*
Molecular Sequence Data
Chemical
Reg. No./Substance:
0/Amino Acids; 0/Escherichia coli Proteins; 498-19-1/Homoserine; EC 2.3.1.46/Homoserine O-Succinyltransferase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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