Action of phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis is significantly influenced by coexisting lipids in substrate-detergent micelles.
The effects of phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (SM), and cholesterol on the activity of phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis were studied in detail in phosphatidylinositol (PI)/detergent mixed micelles. By addition of PC, the enzymatic hydrolysis of PI was significantly stimulated in PI/Triton X-100 as well as PI/sodium deoxycholate (SDC) mixed micelles. SM stimulated enzyme activity toward PI/Triton X-100 micelles at a lower molar ratio of SM to PI, but was rather inhibitory at a ratio higher than 2.0. The enzyme activity became significantly lower with an increase of PE or cholesterol in PI/Triton X-100 micelles. Actually, both PE and cholesterol were intensively inhibitory when added at a higher molar ratio to PI in Triton X-100-containing micelles. In the system of PI/SDC mixed micelles, not only PC but also SM, PE and cholesterol enhanced the enzymatic hydrolysis of PI. The difference between PI/Triton X-100 and PI/SDC micelles regarding the effects of these lipids on PI-PLC action, must be dependent on the physical state of micelles formed by these detergents and lipids.
Kume
T
T
Faculty of Pharmaceutical Sciences, Nagoya City University, Aichi, Japan.
Taguchi
R
R
Ikezawa
H
H
D001413:Bacillus thuringiensis / Q000201:enzymology*; D003902:Detergents; D008055:Lipids / Q000494:pharmacology*; D008823:Micelles; D010716:Phosphatidylinositols / Q000378:metabolism*; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000378:metabolism*
D003902:Detergents; D008055:Lipids; D008823:Micelles; D010716:Phosphatidylinositols; D010738:Type C Phospholipases