Bi-directional control of sphingolmyelinase activity and surface topography in lipid monolayers.

FANANI, M. L.; HÄRTEL, S.; RAFAEL GUSTAVO OLIVEIRA; BRUNO, M.

BIOPHYSICAL JOURNAL

Biophysical Society

Año: 2002 vol. 83 p. 3416 - 3416

0006-3495

ipid 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 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 t