Linked Life Data

9989227

Source:http://linkedlifedata.com/resource/pubmed/id/9989227

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1999-3-2
pubmed:abstractText
Wild-type human butyrylcholinesterase (BuChE) has a non-Michaelian behaviour showing substrate activation with butyrylthiocholine (BTC) as the substrate. The D70G mutant has a catalytic constant identical to that of the wild-type enzyme, but a 10-fold lower affinity for BTC compared to wild-type enzyme, and it does not exhibit activation by excess BTC under conventional conditions. In the present work it was found that addition of polyols or sugars changed the kinetic behaviour of the D70G mutant with BTC. In the presence of 40% sucrose, the D70G mutant enzyme displayed marked activation by excess substrate. Because D70 is hydrogen bonded to Y332, mutants of Y332 were studied. Mutant Y332F had a behaviour similar to that of wild-type BuChE, whereas mutants Y332A, Y332A/D70G and D70G had negligible substrate activation. The behavior of wild-type, Y332F, Y332A and Y332A/D70G did not change in the presence of high concentrations of sugar. Substrate activation has been explained by binding of a second substrate molecule in the peripheral site at D70. The D70G mutant should be incapable of substrate activation, if D70 were the only residue involved in substrate activation. The ability of the D70G mutant to display substrate activation by medium engineering suggests that other residues are involved in initial substrate binding and activation by excess substrate. Osmolyte-induced change in conformation and/or hydration status of Y332 and other solvent-exposed residues may account for the non-Michaelian behaviour of the D70G mutant.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0006-3002
pubmed:author
pubmed:issnType
Print
pubmed:day
11
pubmed:volume
1429
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
422-30
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Polyol-induced activation by excess substrate of the D70G butyrylcholinesterase mutant.
pubmed:affiliation
Centre de Recherches du Service de Santé des Armées, Unité d'Enzymologie, La Tronche, France.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't