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8333238 
Journal Article 
Functional and structural changes induced by phospholipase C in intact mitochondria and submitochondrial particles 
Viola, E; Strinna, E; Bragadin, M; Azzone, GF 
1976 
1 
Biochimica et Biophysica Acta. Biomembranes
ISSN: 0005-2736
EISSN: 1879-2642 
433 
2 
318-332 
English 
1. (1) Phospholipase C from Bacillus cereus causes uncoupling both in intact mitochondria and sonic particles. The uncoupling effect in intact mitochondria occurs parallel to the loss of osmotic properties, while in particles there is an inhibition of membrane bound enzymes. The kinetics of phospholipid hydrolysis and uncoupling are preceeded by a lag phase in mitochondria but not in particles. 2. (2) The extent of phospholipid hydrolysis by acid-base titratin is 55% and 43% in mitochondria and particles, respectively. Chemical analysis gives an extent of hydrolysis of 38% and 30%, respectively. The degree of hydrolysis of phosphatidylcholine and phosphatidylethanolamine is the same in mitochondria and particles. Cardiolipin is not hydrolyzed. 3. (3) Fatty acids with spin label near the phospholipid polar heads indicate the formation of fluid hydrophobic regions in mitochondria. Also the pyrene fluorescence indicates an increased fluidity in mitochondria. In addition the phospholipase C attack is accompanied both in mitochondria and particles by an apparent increased immobilization of the spin label. 4. (4) The data are discussed in terms of the structural differences between mitochondria and particles and of a dual role of phospholipids in controlling enzymatic activities and osmotic properties. © 1976.