Synergistic effect of magnesium and calcium ions in the activation of phospholipase A2 of liver macrophages.
In cell-free extracts of rat liver macrophages (Kupffer cells) phospholipase A2 was found to be strongly activated at free Ca2+ concentrations from 100 nM to 1 microM in the presence of 4 mM free Mg2+. This is within the range of intracellular free Ca2+ reported for basal and various stimulated conditions, respectively. Ca2+ alone increased phospholipase A2 activity at high Ca2+ concentrations (1 mM) whereas Mg2+ alone had only little stimulatory effect. Calmodulin does not seem to participate in the regulation of phospholipase A2 although it relieved the inhibition of phospholipase A2 activity by calmodulin antagonists.
Krause
H
H
Biochemisches Institut, Albert-Ludwigs-Universität, Freiburg, Germany.
Dieter
P
P
Schulze-Specking
A
A
Ballhorn
A
A
Ferber
E
E
Decker
K
K
D000818:Animals; D002118:Calcium / Q000008:administration & dosage*; D002147:Calmodulin / Q000502:physiology; D002413:Cations, Divalent; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D007728:Kupffer Cells / Q000201:enzymology*; D008274:Magnesium / Q000008:administration & dosage*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D051381:Rats
D002147:Calmodulin; D002413:Cations, Divalent; D010741:Phospholipases A; D054467:Phospholipases A2; D008274:Magnesium; D002118:Calcium