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Sphingomyelinases (SMases) hydrolyze the membrane constituent sphingomyelin (SM) to phosphocholine and ceramide (Cer). Growing evidence supports that SMase-induced SM-->Cer conversion leads to the formation of lateral Cer-enriched domains which drive structural reorganization in lipid membranes. We previously provided visual evidence in real-time for the(More)
Lipid lateral organization is increasingly found to modulate membrane-bound enzymes. We followed in real time the reaction course of sphingomyelin (SM) degradation by Bacillus cereus sphingomyelinase (SMase) of lipid monolayers by epifluorescence microscopy. There is evidence that formation of ceramide (Cer), a lipid second messenger, drives structural(More)
We investigated the ways in which phospholipase A2 and sphingomyelinase are mutually modulated at lipid interfaces. The activity of one enzyme is affected by its own reaction products and by substrates and products of the other enzyme; all this depends differently on the lateral surface pressure. Ceramide inhibits both the sphingomyelinase activity rate and(More)
The sphingomyelinase (Sphmase) activity degrading sphingomyelin (Sphm) monolayers shows a slow-reaction latency period before exhibiting constant rate catalysis. These two kinetic regions are regulated independently by the lateral surface pressure and by lipids that are biomodulators of cell function such as ceramide, glycosphingolipids, fatty acids, and(More)
Sphingomyelinase activity against pure sphingomyelin monolayers is constant up to a surface pressure of 18 mN/m and falls above it. Sphingomyelinase- and phospholipase A2-mediated phosphohydrolytic pathways are mutually modulated by the presence of their respective substrates and products. At 15 mN/m non-substrate lipids such as ceramide at a mole fraction(More)
The lipids and proteins of biomembranes exhibit highly dissimilar conformations, geometrical shapes, amphipathicity, and thermodynamic properties which constrain their two-dimensional molecular packing, electrostatics, and interaction preferences. This causes inevitable development of large local tensions that frequently relax into phase or compositional(More)
Ascorbyl palmitate (ASC16) is an anionic amphiphilic molecule of pharmacological interest due to its antioxidant properties. We found that ASC16 strongly interacted with model membranes. ASC16 penetrated phospholipid monolayers, with a cutoff near the theoretical surface pressure limit. The presence of a lipid film at the interface favored ASC16 insertion(More)
Biomembranes contain a wide variety of lipids and proteins within an essentially two-dimensional structure. The coexistence of such a large number of molecular species causes local tensions that frequently relax into a phase or compositional immiscibility along the lateral and transverse planes of the interface. As a consequence, a substantial(More)
In recent years, new evidence in biomembrane research brought about a holistic, supramolecular view on membrane-mediated signal transduction. The consequences of sphingomyelinase (SMase)-driven formation of ceramide (Cer) at the membrane interface involves reorganization of the lateral membrane structure of lipids and proteins from the nm to the mum level.(More)
Diacylglycerol kinase (DGK) isoforms alpha and zeta were extracted from transfected cells that overexpressed these enzymes. We determined the lipid dependence of the binding of these isoforms to liposomes. The modulation by lipid of the rate of phosphorylation of diacylglycerol by these enzymes was also measured. Incorporation of phosphatidylethanolamine(More)