Bimodal regulatory effect of melittin and phospholipase A2-activating protein on human type II secretory phospholipase A2

✍ Scribed by K Koumanov; A Momchilova; C Wolf

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 177 KB
• Volume: 27
• Category: Article
• ISSN: 1065-6995
• DOI: 10.1016/s1065-6995(03)00176-8

✦ Synopsis

Melittin and phospholipase A 2 -activating protein (PLAP) are known as efficient activators of secretory phospholipase A 2 (sPLA 2 ) types I, II, and III when phospholipid liposomes are used as substrate. The present study demonstrates that both peptides can either inhibit or activate sPLA 2 depending on the peptide/phospholipid ratio when erythrocyte membranes serve as a biologically relevant substrate. Low concentrations of melittin and PLAP were observed to inhibit sPLA 2 -triggered release of fatty acids from erythrocyte membranes. The inhibition was reversed at melittin concentrations above 1 µM. PLAP-induced inhibition of sPLA 2 persisted steadily throughout the used concentration range (0-150 nM). The two peptides induced a dose-dependent activation of sPLA 2 at low concentrations, followed by inhibition when model membranes were used as substrate. This opposite modulatory effect on biological membranes and model membranes is discussed with respect to different mechanisms the interaction of the regulatory peptides with the enzyme molecules and the substrate vesicles.