Linked Life Data

4016097

Source:http://linkedlifedata.com/resource/pubmed/id/4016097

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
8
pubmed:dateCreated
1985-9-16
pubmed:abstractText
In the biosynthesis of the cyclic decapeptide antibiotic gramicidin S, the constituent amino acids are activated by a two-step mechanism involving aminoacyl adenylate and thio ester formation which are both reversible processes. The dissociation constants (KD) for the gramicidin S synthetase-substrate amino acid-thio ester complexes are 100-1000-fold lower compared to the KM data of the preceding aminoacyl adenylate reactions. The affinity for these substrates is appreciably higher at the thio template sites than at the aminoacyl adenylate reaction centers. Therefore, the activation equilibria are quantitatively shifted toward thio ester formation. A set of thermodynamic parameters for the activation processes was determined from the temperature dependence of the KM and KD data. Reaction enthalpies were obtained from a van't Hoff analysis of these constants. delta G degree for the substrate activation reactions of the heavy enzyme of gramicidin S synthetase (GS 2) is predominantly controlled by entropy contributions. In contrast, the overall activation and concomitant racemization of phenylalanine by phenylalanine racemase (GS 1) are exothermic processes which are distinguished by a small negative reaction entropy.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
9
pubmed:volume
24
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2022-7
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1985
pubmed:articleTitle
Gramicidin S synthetase. Temperature dependence and thermodynamic parameters of substrate amino acid activation reactions.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't