Bidirectional control of sphingomyelinase activity and surface topography in lipid monolayers. Biophysical journal, 83(6), 3416-3424.<\/p>\n\n\n\n
Fanani, M. L., H\u00e4rtel, S., Oliveira, R. G., & Maggio, B. (2002).<\/p>\n\n\n\n
ABSTRACT<\/strong>
Lipid lateral organization is increasingly found to modulate membrane-bound enzymes. We followed in real time the reaction course of sphingomyelin (SM) degradation by\u00a0Bacillus cereus<\/em>\u00a0sphingomyelinase (SMase) of lipid monolayers by epifluorescence microscopy. There is evidence that formation of ceramide (Cer), a lipid second messenger, drives structural reorganization of membrane lipids. Our results provide visual evidence that SMase activity initially alters surface topography by inducing phase separation into condensed (Cer-enriched) and expanded (SM-enriched) domains. The Cer-enriched phase grows steadily as the reaction proceeds at a constant rate. The surface topography derived from the SMase-driven reaction was compared with, and found to differ from, that of premixed SM\/Cer monolayers of the same lipid composition, indicating that substantial information content is stored depending on the manner in which the surface was generated. The long-range topographic changes feed back on the kinetics of Smase, and the onset of condensed-phase percolation is temporally correlated with a rapid drop of reaction rate. These observations reveal a bidirectional influence and communication between effects taking place at the local molecular level and the supramolecular organization. The results suggest a novel biocatalytic-topographic mechanism in which a surface enzymatic activity can influence the function of amphitropic proteins important for cell function.<\/p>\n\n\n\n