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Effects of phospholipids on sphingomyelin hydrolysis induced by intestinal alkaline sphingomyelinase: an in vitro study.
MedLine Citation:
PMID:  10827341     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Digestion of dietary sphingomyelin (SM) is catalyzed by intestinal alkaline sphingomyelinase (SMase) and may have important implications in colonic tumorigenesis. Previous studies demonstrated that the digestion and absorption of dietary SM was slow and incomplete and that the colon was exposed to SM and its hydrolytic products including ceramide. In the present work, we studied the influences of glycerophospholipids and hydrolytic products of phosphatidylcholine (PC; i.e., lyso-PC, fatty acid, diacylglycerol, and phosphorylcholine) on SM hydrolysis induced by purified rat intestinal alkaline SMase in the presence of 10 mM taurocholate. It was found that various phospholipids including PC, phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylethanolamine (PE), and phosphatidic acid (PA) inhibit alkaline SMase activity in a dose-dependent manner, with the degree of inhibition being in the order PA > PS > PI > PC > PE. Similar inhibition was also seen in a buffer of pH 7.4, which is close to the physiologic pH in the middle of the small intestine. When the effects of hydrolytic products of PC were studied, lyso-PC, oleic acid, and 1,2-dioleoyl glycerol also inhibited alkaline SMase activity, whereas phosphorylcholine enhanced SMase activity. However, in the absence of bile salt, acid phospholipids including PA, PS, and PI mildly stimulated alkaline SMase activity whereas PC and PE had no effect. It is concluded that in the presence of bile salts, glycerophospholipids and their hydrolytic products inhibit intestinal alkaline SMase activity. This may contribute to the slow rate of SM digestion in the upper small intestine.
J J Liu; A Nilsson; R D Duan
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Journal of nutritional biochemistry     Volume:  11     ISSN:  0955-2863     ISO Abbreviation:  J. Nutr. Biochem.     Publication Date:  2000 Apr 
Date Detail:
Created Date:  2004-06-21     Completed Date:  2005-03-22     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9010081     Medline TA:  J Nutr Biochem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  192-7     Citation Subset:  -    
Department of Cell Biology 1, University Hospital of Lund, Lund, Sweden.
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