Linked Life Data

3745162

Source:http://linkedlifedata.com/resource/pubmed/id/3745162

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
25
pubmed:dateCreated
1986-10-15
pubmed:abstractText
H2(18)O isotope exchange into specifically 13C-labeled substrate was used to obtain information on the rate-limiting step in the action of the phospholipase A2 from the venom of the Indian cobra (Naja naja naja). Incorporation of 18O was detected by the effect of 18O on 13C chemical shifts in 13C NMR. The enzymatic hydrolysis of a micellar phosphatidylcholine analogue of platelet-activating factor 1-alkyl-2-[1-13C]lauroyl-sn-glycero-3-phosphorylcholine proceeds by an O-acyl cleavage of the sn-2 ester bond. The reaction was examined for simultaneous 18O incorporation into the substrate. No exchange was found, suggesting that the hydrolytic step is not followed by a higher energy transition state and that it or a step before it appears to be rate-limiting. Previous experiments on phosphatidylethanolamine activation indicate that kcat is altered but that the km remains the same upon activation, suggesting that the binding steps occurring before the hydrolytic step are not affected. This strongly suggests that the hydrolytic step is in fact the rate-limiting step under these conditions. The 13C, 18O NMR technique should be generally applicable to mechanistic questions of this type.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
261
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
11663-6
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1986
pubmed:articleTitle
Rate-determining step in phospholipase A2 mechanism. 18O isotope exchange determined by 13C NMR.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.