Polylysine and polyamine stimulation of the phosphatidylinositol kinases of amphibian oocyte membranes.
Phosphatidylinositol kinase present in Xenopus laevis oocyte membranes catalyzes the formation of phosphatidylinositol 4-phosphate using phosphatidylinositol and ATP as substrates while the activity of a second enzyme, phosphatidylinositol-4-phosphate kinase, results in the synthesis of phosphatidylinositol 4,5-bisphosphate. Large (Mr greater than 20,000) homopolymers of L-lysine or L-ornithine can stimulate the activity of both of these enzymes by at least 2-fold at 10-20 microM concentrations. Under similar conditions poly-L-arginine fails to stimulate the reaction causing a partial inhibition. Smaller polylysine (25 lysines) or lysine-rich oligopeptides such as one corresponding to the last 14 amino acids of the carboxyl end of c-Ki-ras 2 protein produce appreciable stimulation of phosphatidylinositol but at concentrations of 300-500 microM. Spermine and spermidine at millimolar concentrations also stimulate exogenous phosphatidylinositol phosphorylation. The amino-glycoside antibiotic neomycin has a biphasic effect, stimulating the phosphatidylinositol kinase at concentrations below 0.5 mM and strongly inhibiting at higher concentrations. Polylysine also moderately stimulates the loss of radioactivity of phosphatidylinositol-4-[32P] phosphate observed in oocyte membranes. Polylysine and polyornithine do not change the apparent Km for ATP of the phosphatidylinositol kinase but increase the Vmax of the reaction.
Carrasco
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Departamento de Bioquimica, Facultad de Medicina, Universidad de Chile, Santiago.
Jacob
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G
Allende
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CC
Allende
J E
JE
D019870:1-Phosphatidylinositol 4-Kinase; D000818:Animals; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008970:Molecular Weight; D009865:Oocytes / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism*; D011073:Polyamines / Q000494:pharmacology*; D011107:Polylysine / Q000494:pharmacology*; D014982:Xenopus laevis
D010716:Phosphatidylinositols; D011073:Polyamines; D011107:Polylysine; D010770:Phosphotransferases; D019870:1-Phosphatidylinositol 4-Kinase