Document Detail

Characterization of human acid sphingomyelinase purified from the media of overexpressing Chinese hamster ovary cells.
MedLine Citation:
PMID:  10407147     Owner:  NLM     Status:  MEDLINE    
A rapid purification method was developed to isolate milligram quantities of human acid sphingomyelinase from the media of overexpressing Chinese hamster ovary cells. The purified, recombinant enzyme (rhASM) had physical and kinetic characteristics that were consistent with those reported for the non-recombinant enzyme, including an acidic pH optimum and sensitivity to sulfhydryl reducing reagents and the zinc specific chelator, 1, 10-phenanthroline. A novel assay using fluorescently conjugated sphingomyelin was developed to explore the substrate binding properties of rhASM. Substrate binding required a fatty acid chain length of at least six carbons and the presence of the phosphocholine headgroup on sphingomyelin. Substrate binding also required an acidic pH, and was inhibited by pretreatment of the enzyme with sulfhydral reducing reagents or 1,10-phenanthroline. rhASM was rapidly internalized by cultured skin fibroblasts from Niemann-Pick disease (NPD) patients, and approximately 50% of this uptake was dependent on the mannose 6-phosphate receptor system. Studies using FITC-labeled rhASM revealed that by 1 h the internalized enzyme was localized to acidic compartments and could degrade sphingomyelin, the first demonstration that a lysosomal sphingolipid hydrolase can be fluorescently labeled and retain its biological activity. Intravenous injection of rhASM into ASM knock-out mice showed that the t(1/2) in the plasma was less than 5 min, and that the majority of the injected enzyme was taken up by the liver, followed by the spleen. Thus, these studies lay the foundation for future structure/function investigations of ASM, further investigations into this enzyme's role in ceramide mediated signal transduction, and the evaluation of enzyme replacement therapy for NPD using the mouse model.
X He; S R Miranda; X Xiong; A Dagan; S Gatt; E H Schuchman
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1432     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1999 Jul 
Date Detail:
Created Date:  1999-08-20     Completed Date:  1999-08-20     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  251-64     Citation Subset:  IM    
Department of Human Genetics, Box 1498, Mount Sinai School of Medicine, 1425 Madison Avenue, Room 14-20A, New York, NY 10029, USA.
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MeSH Terms
CHO Cells / enzymology*
Culture Media / chemistry
Dithiothreitol / pharmacology
Fibroblasts / metabolism
Mice, Knockout
Niemann-Pick Diseases / metabolism
Phenanthrolines / pharmacology
Recombinant Proteins / chemistry
Sphingomyelin Phosphodiesterase / chemistry,  isolation & purification*,  pharmacology
Tissue Distribution
Grant Support
Reg. No./Substance:
0/Culture Media; 0/Phenanthrolines; 0/Recombinant Proteins; 3326-32-7/Fluorescein-5-isothiocyanate; 3483-12-3/Dithiothreitol; 66-71-7/1,10-phenanthroline; EC 3.1.4.-/acid sphingomyelinase-1; EC Phosphodiesterase

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