Linked Life Data

1899028

Source:http://linkedlifedata.com/resource/pubmed/id/1899028

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1991-2-28
pubmed:abstractText
The physiological synthesis of L-tryptophan from indoleglycerol phosphate and L-serine catalyzed by the alpha 2 beta 2 bienzyme complex of tryptophan synthase requires spatial and dynamic cooperation between the two distant alpha and beta active sites. The carbanion of the adduct of L-tryptophan to pyridoxal phosphate accumulated during the steady state of the catalyzed reaction. Moreover, it was formed transiently and without a lag in single turnovers, and glyceraldehyde 3-phosphate was released only after formation of the carbanion. These and further data prove first that the affinity for indoleglycerol phosphate and its cleavage to indole in the alpha subunit are enhanced substantially by aminoacrylate bound to the beta subunit. This indirect activation explains why the turnover number of the physiological reaction is larger than that of the indoleglycerol phosphate cleavage reaction. Second, reprotonation of nascent tryptophan carbanion is rate limiting for overall tryptophan synthesis. Third, most of the indole generated in the active site of the alpha subunit is transferred directly to the active site of the beta subunit and only insignificant amounts pass through the solvent. Comparison of the single turnover rate constants with the known elementary rate constants of the partial reactions catalyzed by the alpha and beta active sites suggests that the cleavage reaction rather than the transfer of indole or its condensation with aminoacrylate is rate limiting for the formation of nascent tryptophan.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
30
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
479-84
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Mechanism of the physiological reaction catalyzed by tryptophan synthase from Escherichia coli.
pubmed:affiliation
Abteilung Biophysikalische Chemie, Biozentrum der Universität Basel, Switzerland.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't