Identification of high molecular weight forms of inositol 1,4,5-trisphosphate 3-kinase in rat thymus and human lymphocytes.
A soluble inositol 1,4,5-trisphosphate 3-kinase (InsP3 3-kinase) has been characterized from extracts of rat thymus. The enzyme was shown to have a molecular weight within the range 98,000-114,000 M(r) as determined by regeneration of enzyme activity from sodium dodecyl sulphate polyacrylamide gels. The enzyme phosphorylates inositol 1,4,5-trisphosphate (InsP3) to inositol 1,3,4,5-tetrakisphosphate (InsP4) with an apparent Km of 3.1 +/- 0.4 microM. The enzyme is stimulated 4-6-fold by Ca2+/calmodulin and is not recognised by polyclonal antisera raised against rat brain InsP3 3-kinase A. High levels of InsP3 3-kinase activity were also detected in soluble extracts of human lymphocyte preparations. The human lymphocyte enzyme was shown to have a molecular weight between 61,000 and 70,000 M(r) as judged by SDS-PAGE, and was stimulated approximately 10-fold in the presence of Ca2+/calmodulin. These results establish that InsP3 3-kinase from rat thymus and human lymphocyte preparations represent high molecular weight isoenzymes of the InsP3 3-kinase family.
D'Santos
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CS
Institute of Interdisciplinary Research (IRIBHN), School of Medicine, Free University of Brussels (U.L.B.), Belgium.
Communi
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Ludgate
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Vanweyenberg
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Takazawa
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Erneux
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D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism; D007527:Isoenzymes / Q000032:analysis* / Q000302:isolation & purification; D007700:Kinetics; D008214:Lymphocytes / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000032:analysis* / Q000302:isolation & purification; D051381:Rats; D017208:Rats, Wistar; D013950:Thymus Gland / Q000201:enzymology*
D002147:Calmodulin; D007295:Inositol Phosphates; D007527:Isoenzymes; C081655:inositol-1,3,4,5-tetrakisphosphate; D015544:Inositol 1,4,5-Trisphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase; D002118:Calcium