Linked Life Data

9709000

Source:http://linkedlifedata.com/resource/pubmed/id/9709000

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
33
pubmed:dateCreated
1998-9-10
pubmed:abstractText
Phosphatidylcholine phospholipase C (EC 3.1.4.3) from Bacillus cereus has been assayed with substrates in the form of large unilamellar vesicles. Phosphatidylcholine, phosphatidylethanolamine (also a substrate for the enzyme), sphingomyelin, and cholesterol have been mixed in various proportions, in binary, ternary, and quaternary mixtures. A lag period, followed by a burst of enzyme activity, has been found in all cases. The activity burst was always accompanied by an increase in turbidity of the vesicle suspension. Varying lipid compositions while keeping constant all the other parameters leads to a range of lag times extending over 2 orders of magnitude (from 0.13 to 38.0 min), and a similar variability is found in maximal enzyme rates (from 0.40 to 55.9 min-1). Meanwhile, the proportion of substrate that is hydrolyzed during the lag period remains relatively constant at 0.10% moles of total lipid, in agreement with the idea that enzyme activation is linked to vesicle aggregation through diacylglycerol-rich patches. Phosphatidylethanolamine and cholesterol enhance the enzyme activity in a dose-dependent way: they reduce the lag times and increase the maximal rates. The opposite is true of sphingomyelin. These lipids exert each its own peculiar effect, positive or negative, either alone or in combination, so that the susceptibility of a given mixture to the enzyme activity can be to some extent predicted from its composition. Phospholipase C activity is not directly influenced by the formation of nonlamellar structures. However, the presence of lipids with a tendency to form nonlamellar phases, such as phosphatidylethanolamine or cholesterol, stimulates the enzyme even under conditions at which purely lamellar phases exist. Conversely sphingomyelin, a well-known stabilizer of the lamellar phase, inhibits the enzyme. Thus phospholipase C appears to be regulated by the overall geometry and composition of the bilayer.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
18
pubmed:volume
37
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
11621-8
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Phospholipase C hydrolysis of phospholipids in bilayers of mixed lipid compositions.
pubmed:affiliation
Grupo Biomembranas (Unidad Asociada al C.S.I.C.), Departamento de Bioquímica, Universidad del País Vasco, Bilbao, Spain.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't