ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract— Activity of cholesterol ester hydrolase localized almost exclusively in the myelin sheath (Eto & Suzuki, 1973a) was greatly affected by exogenous lipids added to the assay mixture. With isolated myelin as the enzyme source, phosphatidylserine was most effective in stimulating the activity. Other phospholipids were less effective. Efhanolamine phospholipid was slightly inhibitory and lysolecithin was strongly inhibitory. Differences in the fatty acid composition did not appear to account for such different effects. Glucosylceramide, galactosylceramide and digalactosylceramide were stimulatory while sulfatide, ganglioside and its asialo-derivative were inhibitory. Saturated fatty acids were generally stimulatory while corresponding unsaturated acids were strongly inhibitory. In order for exogenous lipids to be effective they had to be added to the assay mixture as free dispersion. When heat-inactivated myelin was used as the lipid source, no effect was observed, while equivalent amounts of a whole white matter lipid mixture was effective. Although phosphatidylserine was the most effective activator among the lipids tested, it could not completely replace sodium taurocholate present in the standard assay system. When isolated myelin was stored frozen, the activity of the enzyme declined gradually in the standard system without additional lipids. The stimulating effect of phosphatidylserine was greater for such partially inactivated enzyme sources, although it did not completely restore the activity to that of fresh preparations. When myelin was fractionated into basic protein, proteolipid protein and the high molecular weight acidic protein (Wolfgram) fractions, the last fraction contained most of the recovered activity. However, Wolfgram protein was less active than the intact myelin when assayed without additional lipid. The addition of phosphatidylserine completely restored the activity of this partially delipidated preparation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1976.tb05147.x
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