Phosphatidylinositol breakdown by subcellular preparations of small lymphocytes from pig mesenteric lymph nodes was investigated. Activity was higher than in preparations from the tissues studied previously; it was recovered largely in the soluble fraction, which showed pH optima at both 5.4–5.6 and 7.0–7.3. As in other tissues, phosphatidylinositol cleavage produced 1,2-diacylglycerol and a mixture of myo-inositol 1:2-cyclic phosphate and myo-inositol 1-phosphate. It was stimulated by addition of CaCl2 and, less effectively, by MgCl2. On sucrose-density-gradient ultracentrifugation at pH7.0 two peaks of activity were observed (approx. sedimentation coefficients 8S and 10S); the activity profiles on the gradients were similar when assayed at pH7.0 and 5.5. Activity at pH7.0 (and 0.4mm-CaCl2) was decreased by agents, such as salts and lipophilic cations, which tend to neutralize the negative charge of phosphatidylinositol; at pH5.5 these agents slightly stimulated activity. It is suggested that the same enzyme(s) may be responsible for activity at both pH optima and that previous workers may have underestimated the pH7.0 activity because of the inhibitory influence of cations under the usual assay conditions.
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September 1974
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Research Article|
September 01 1974
Phosphatidylinositol cleavage catalysed by the soluble fraction from lymphocytes. Activity at pH5.5 and pH7.0 Available to Purchase
David Allan;
David Allan
1Department of Biochemistry, University of Birmingham, P.O. Box 363, Birmingham B15 2TT, U.K.
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Robert H. Michell
Robert H. Michell
1Department of Biochemistry, University of Birmingham, P.O. Box 363, Birmingham B15 2TT, U.K.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1974 London: The Biochemical Society
1974
Biochem J (1974) 142 (3): 591–597.
Citation
David Allan, Robert H. Michell; Phosphatidylinositol cleavage catalysed by the soluble fraction from lymphocytes. Activity at pH5.5 and pH7.0. Biochem J 1 September 1974; 142 (3): 591–597. doi: https://doi.org/10.1042/bj1420591
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