title: Purification, localization, and expression of human intestinal alkaline sphingomyelinase.
abstract: Sphingomyelin (SM) metabolism in the gut may have an impact on colon cancer development. In this study, we purified alkaline sphingomyelinase (alk-SMase) from human intestinal content, and studied its location in the mucosa, expression in colon cancer, and function on colon cancer cells. The enzyme was purified by a series of chromatographies. The molecular mass of the enzyme is 60 kDa, optimal pH is 8.5, and isoelectric point is 6.6. Under optimal conditions, 1 mg of the enzyme hydrolyzed 11 mM SM per hour. The properties of the enzyme are similar to those of rat intestinal alk-SMase but not to those of bacterial neutral SMase. Immunogold electronmicroscopy identified the enzyme on the microvillar membrane in endosome-like structures and in the Golgi complexes of human enterocytes. The expression and the activity of the enzyme were decreased in parallel in human colon cancer tissues compared with the adjacent normal tissue. The enzyme inhibited DNA biosynthesis and cell proliferation dose dependently and caused a reduction of SM in HT29 cells. Intestinal alk-SMase is localized in the enterocytes, down-regulated in human colon cancer, and may have antiproliferative effects on colon cancer cells.
authors.affiliation: Gastroenterology Laboratory, Biomedical Center, B11, University of Lund, S-221 84 Lund, Sweden. rui-dong.duan@med.lu.se
authors.forename: Rui-Dong
authors.initials: RD
authors.lastname: Duan
authors.forename: Yajun
authors.initials: Y
authors.lastname: Cheng
authors.forename: Gert
authors.initials: G
authors.lastname: Hansen
authors.forename: Erik
authors.initials: E
authors.lastname: Hertervig
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Liu
authors.forename: Ingvar
authors.initials: I
authors.lastname: Syk
authors.forename: Hans
authors.initials: H
authors.lastname: Sjostrom
authors.forename: Ake
authors.initials: A
authors.lastname: Nilsson
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000201:enzymology / Q000473:pathology; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D020895:Enterocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology; D007422:Intestines / Q000201:enzymology*; D007525:Isoelectric Focusing; D008970:Molecular Weight; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D013109:Sphingomyelins / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D013109:Sphingomyelins; D004247:DNA; D013108:Sphingomyelin Phosphodiesterase