Digestion of ceramide by human milk bile salt-stimulated lipase

摘要: BACKGROUNDThere is a renewed interest in metabolism of sphingolipids because their role signal transduction. Sphingomyelin the dominating phospholipid human milk but its and possible function gastrointestinal tract breast fed infants unknown. We explored whether bile salt-stimulated lipase has sphingolipid metabolism.METHODSIn vitro assays sphingomyelinase ceramidase activities, using radiolabeled substrates, samples purified native recombinant variants with or without known activators inhibitors.RESULTSHuman whey catalysed hydrolysis palmitoyl-labeled ceramide highest rate around pH 8.5-9.0. 1 mg hydrolysed 0.7 micromol one hour at 8.5 presence 4 mM salt. The activity was inhibited by antibodies towards lipase, indicating that this accounted for virtually all milk. In contrast, showed no against sphingomyelin. However we give evidence separate, hitherto unknown, acid Under used conditions could account half sphingomyelin hour.CONCLUSIONSHuman hydrolyses may thus have digestion, only after initial to phosphorylcholine. Part latter be carried out stomach now described. speculate these two enzymes importance optimal use sphingolipids. (Less)