Linked Life Data

2952897

Source:http://linkedlifedata.com/resource/pubmed/id/2952897

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1987-5-28
pubmed:abstractText
A high affinity Ca2+/Mg2+ ATPase has been identified and localized in synaptic membrane subfractions. This enzyme is stimulated by low concentrations of Ca2+ (less than or equal to microM) believed to approximate the range of Ca2+ in the synaptosomal cytosol (0.1 to 5.0 microM). The opiate agonist levorphanol, in a concentration-dependent fashion, inhibited Ca2+-stimulated ATP hydrolysis in lysed synaptic membranes. This inhibition was reversed by naloxone, while dextrorphan, the inactive opiate isomer, was without effect. Inhibition by levorphanol was most pronounced in a subfraction of synaptic membranes (SPM-1). The inhibition of Ca2+-stimulated ATP hydrolysis was characterized by a reduction in Vmax for Ca2+. Levorphanol pretreatment reduced the Hill coefficient (HN) of 1.5 to 0.7, suggesting cooperative interaction between the opiate receptor and the enzyme protein. Levorphanol, but not dextrorphan, also inhibited (28%) ATP-dependent Ca2+ uptake by synaptic membranes. Opiate ligand stereoisomers were tested for their effects on calmodulin stimulating of high affinity Ca2+/Mg2+ ATPase in synaptic membranes. Levorphanol (10 microM), but not the inactive stereoisomer (+)dextrorphan, significantly inhibited (35%) the calmodulin-activated Ca2+-dependent ATP hydrolysis activity in a preparation of lysed synaptic membranes. Both Ca2+-dependent and calmodulin-dependent stimulation of the enzyme in the presence of optimal concentrations of the other co-substrate were inhibited by levorphanol (35-40%) but not dextrorphan. Inhibition of ATP hydrolysis was characterized by a reduction in Vmax for both Ca2+ and calmodulin stimulation of the enzyme. Calmodulin stimulation of enzyme activity was most pronounced in SPM-1, the membrane fraction which also exhibits the maximal opiate inhibition (40%) of the Ca2+-ATPase.(ABSTRACT TRUNCATED AT 250 WORDS)
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0364-3190
pubmed:author
pubmed:issnType
Print
pubmed:volume
12
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
41-8
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed:year
1987
pubmed:articleTitle
Opiates inhibit calmodulin activation of a high-affinity Ca2+-stimulated Mg2+-dependent ATPase in synaptic membranes.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.