PLA2 activity in Tetrahymena pyriformis. Effects of inhibitors and stimulators.
Phospholipase A2 (PLA2) is an enzyme which participates in signalling mechanisms cleaving arachidonate from sn-2 position of glycerophospholipids. In this study we have verified the existence of a PLA2-like activity in the free living protozoan, Tetrahymena pyriformis GL. This activity is Ca(2+)-independent, EDTA (10 mM) has no effect on its activity. Quinacrine (0.1 mM) and 4-bromophenacyl bromide (BPB; 0.1 mM) inhibited, melittin (20 micrograms/ml) significantly stimulated the PLA2 activity and the release of free arachidonic acid (AA) from 1-acyl 2-14C-arachidonyl-3-phosphatidylethanolamine substrate. Melittin stimulated PLA2 hyperactivity is CA(2+)-dependent. There was no considerable alteration in the PLA2 activity by stimulation of the activity by tyrosine kinase (with vanadate, H2O2), phospholipase C (PLC) (with phorbol 12, 13-dibutyrate) or G-proteins (with NaF, AlF4), thus in Tetrahymena PLA2 activity seems to be independent of these--in Tetrahymena (also functioning)--signalling pathways. Treatment with quinacrine and BPB leads to decreased synthesis and disturbed breakdown of phospholipids and phosphoinositides. These findings suggest that PLA2 activity is in connection with the phospholipid metabolism of Tetrahymena.
Kovács
P
P
Semmelweis University of Medicine, Department of Biology, Budapest, Hungary.
Csaba
G
G
D000098:Acetophenones / Q000494:pharmacology; D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005459:Fluorides / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007294:Inositol / Q000378:metabolism; D018021:Lithium Chloride / Q000494:pharmacology; D008555:Melitten / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism; D011505:Protein-Tyrosine Kinases; D011796:Quinacrine / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D012969:Sodium Fluoride / Q000494:pharmacology; D013769:Tetrahymena pyriformis / Q000187:drug effects / Q000201:enzymology*; D014638:Vanadates / Q000494:pharmacology
D000098:Acetophenones; D017607:Aluminum Compounds; D004791:Enzyme Inhibitors; D010716:Phosphatidylinositols; D010743:Phospholipids; D008555:Melitten; D016718:Arachidonic Acid; D015240:Phorbol 12,13-Dibutyrate; D014638:Vanadates; D007294:Inositol; D012969:Sodium Fluoride; D006861:Hydrogen Peroxide; D011505:Protein-Tyrosine Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D018021:Lithium Chloride; D011796:Quinacrine; C006821:4-bromophenacyl bromide; D005459:Fluorides; D002118:Calcium; C032311:aluminum fluoride