Evidence for the presence of multiple forms of Sph kinase in human platelets.
The intracellular distribution of sphingosine (Sph) kinase activity was examined in human platelets. A large proportion (72%) of the total activity was found to be associated with the membrane fraction, and the membrane-associated fraction had higher specific activity compared with the cytosolic enzyme. Most of the membrane-associated activity could be extracted with 1 M NaCl. The cytosolic activity was unstable upon heat treatment, with 80% of the activity being lost during incubation at 45 degreesC for 1 h, whereas the NaCl-extractable fraction was stable under the same conditions. When subjected to Mono Q column chromatography, the cytosolic fraction produced two activity peaks and the NaCl-extractable fraction gave a single peak. These three Sph kinase activities showed different responses to stimulation by beta-octylglucoside and inhibition by N, N-dimethylsphingosine and l-threo-dihydrosphingosine, suggesting the presence of multiple enzyme forms in human platelets.
Department of Biochemistry, Gifu University School of Medicine, Tsukasamachi-40, Gifu 500-8705, Japan. banno@cc.gifu-u.ac.jp
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Banno
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Kato
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Hara
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Nozawa
D001792:Blood Platelets / Q000201:enzymology*; D002457:Cell Extracts; D002462:Cell Membrane / Q000201:enzymology; D002853:Chromatography, Liquid; D003600:Cytosol / Q000201:enzymology; D004795:Enzyme Stability; D005960:Glucosides / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D012965:Sodium Chloride / Q000737:chemistry; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000099157:Sphingosine Kinase
D002457:Cell Extracts; D005960:Glucosides; D007527:Isoenzymes; D017853:Phosphotransferases (Alcohol Group Acceptor); D012965:Sodium Chloride; D013110:Sphingosine; D000099157:Sphingosine Kinase; C018619:octyl-beta-D-glucoside; C061800:N,N-dimethylsphingosine; C005682:safingol