Linked Life Data

14982443

Source:http://linkedlifedata.com/resource/pubmed/id/14982443

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
8
pubmed:dateCreated
2004-2-25
pubmed:abstractText
Chorismate is the end-product of the shikimate pathway for biosynthesis of carbocyclic aromatic compounds in plants, bacteria, fungi, and some parasites. Anthranilate synthase (AS), 4-amino-4-deoxychorismate synthase (ADCS), and isochorismate synthase (IS) are homologous enzymes that carry out the initial transformations on chorismate in the biosynthesis of tryptophan, p-aminobenzoate, and enterobactin, respectively, and are expected to share a common mechanism. Poor binding to ADCS of two potential transition state analogues for addition of a nucleophile to C6 of chorismate implies that it, like AS and IS, initiates reaction by addition of a nucleophile to C2. Molecular modeling based on the X-ray structures of AS and ADCS suggests that the active site residue K274 is the nucleophile employed by ADCS to initiate the reaction, forming a covalent intermediate. The K274A and K274R mutants were shown to have 265- and 640-fold reduced k(cat) values when PabA (the cognate amidotransferase) + glutamine are used as the nitrogen source. Under conditions of saturating chorismate and NH(4)(+), ADCS and the K274A mutant have identical k(cat) values, suggesting the participation of NH(4)(+) as a rescue agent. Such participation was confirmed by the buildup of 2-amino-2-deoxyisochorismate in the reactions of the K274A mutant but not ADCS, when either NH(4)(+) or PabA + glutamine is used as the nitrogen source. Additionally, the inclusion of ethylamine in the reactions of K274A yields the N-ethyl derivative of 2-amino-2-deoxyisochorismate. A unifying mechanism for AS, ADCS, and IS entailing nucleophile addition to C2 of chorismate in an S(N)2' ' process is proposed.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
3
pubmed:volume
126
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2378-85
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2004
pubmed:articleTitle
Conservation of mechanism in three chorismate-utilizing enzymes.
pubmed:affiliation
Department of Chemistry, University of California-Davis, Davis, California 95616, USA.
pubmed:publicationType
Journal Article