At low concentrations of Mg2+, incorporation of 32P from [gamma-32P]ATP into phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) in plasma membranes isolated from human polymorphonuclear leucocytes was enhanced 2-4-fold by the polyamines spermidine and spermine. Polyamines had no effects on inositol phospholipid phosphorylation at high concentrations of Mg2+. At 1 mM-Mg2+, [32P]PIP2 synthesis was maximally enhanced by 2 mM-spermine and 5 mM-spermidine, whereas putrescine only slightly enhanced synthesis. Spermine decreased the EC50 (concn. for half-maximal activity) for Mg2+ in [32P]PIP2 synthesis from 5 mM to 0.5 mM. Spermine did not modulate the Km for ATP for [32P]PIP or [32P]PIP2 synthesis. Spermine also decreased the EC50 for PI in [32P]PIP synthesis. In contrast, spermine elevated the apparent Vmax, without affecting the EC50 for PIP, for [32P]PIP2 synthesis. Spermine and spermidine also inhibited the hydrolysis of [32P]PIP2 by phosphomonoesterase activity. Therefore polyamines appear to activate inositol phospholipid kinases by eliminating the requirements for super-physiological concentrations of Mg2+. Polyamine-mediated inhibition of polyphosphoinositide hydrolysis would serve to potentiate further their abilities to promote the accumulation of polyphosphoinositides in biological systems.
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Research Article|
November 15 1988
Modulation of inositol phospholipid metabolism by polyamines
C D Smith;
C D Smith
1Howard Hughes Medical Institute and the Department of Medicine, Duke University Medical Center, Durham, NC 27710, U.S.A.
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R Snyderman
R Snyderman
1Howard Hughes Medical Institute and the Department of Medicine, Duke University Medical Center, Durham, NC 27710, U.S.A.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1988 London: The Biochemical Society
1988
Biochem J (1988) 256 (1): 125–130.
Citation
C D Smith, R Snyderman; Modulation of inositol phospholipid metabolism by polyamines. Biochem J 15 November 1988; 256 (1): 125–130. doi: https://doi.org/10.1042/bj2560125
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