Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.1 (alkaline phosphatase)
 47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

IL-8 is a neutrophil-specific chemoattractant and cellular activator which exists in at least three forms, 69, 72, and 77 amino acids. The predominant monocyte product has 72 amino acids, whereas endothelial cells secrete the 77-amino acid form. The 72-amino acid form has been shown to increase intracellular calcium in neutrophils, but the exact biochemical pathways involved in stimulation of these cells is unknown. N-formyl peptide chemoattractants in neutrophils stimulate the formation of phosphatidylinositol-4,5-bisphosphate (PIP2), a reservoir for second messenger molecules and regulator of actin assembly through its association with the actin-binding proteins, profilin, and gelsolin. The present study examined whether IL-8 altered the enzyme which synthesizes PIP2, phosphatidylinositol-4-phosphate (PIP) kinase. Incubation of intact neutrophils with 10 nM IL-8 caused approximately a twofold increase in the activity of the enzyme. All forms of IL-8 stimulated PIP kinase activity in concentrations ranging from 1 to 50 nM, and the dose-response curves exactly correlated with the order of potency of these cytokines for interacting with the IL-8R on the surface of neutrophils. Lineweaver-Burk analysis of the kinetics of PIP kinase assayed in the presence of 0.03 to 0.7 mM ATP showed that 10 nM IL-8 increased the Vmax of the enzyme 38 to 70.5%, with no significant change in the apparent Km for ATP or for PIP. The stimulation of PIP kinase activity could not be explained by decreased degradation of PIP2 by phospholipase C or phosphomonoesterase activity in the membranes isolated from cells treated with IL-8 or by a decrease in the degradation of ATP. The microfilament disrupter, cytochalasin b, inhibited IL-8 induced stimulation of PIP kinase. These findings demonstrate that all forms of IL-8 stimulate PIP kinase in human neutrophils. This event may provide molecular signals to these cells that are necessary to maintain or change the state of microfilament assembly during cellular activation.
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PMID:IL-8 stimulates phosphatidylinositol-4-phosphate kinase in human polymorphonuclear leukocytes. 131 31

Phosphatidylinositol 4-phosphate (PIP) kinase (E.C. 2.7.1.68) has been purified about 1200-fold from rat liver plasma membranes, taking advantage of affinity chromatography on quercetin-Sepharose as a novel step. The purified PIP kinase showed no contamination by the following enzyme activities: phosphatidylinositol (PI) kinase (EC 2.7.1.67), protein kinase C (EC 2.7.1.-), diacylglycerol kinase (EC 2.7.1.-), phospholipase C (EC 3.1.4.11), protein-tyrosine kinase (EC 2.7.1.112), alkaline phosphatase (EC 3.1.3.1), triphosphoinositide phosphomonoesterase (EC 3.1.3.36), adenylate kinase (EC 2.7.4.3) and cAMP-dependent protein kinase (EC 2.7.1.37). The liver membrane enzyme requires high Mg2+ concentrations with a KM value of 10 mM. Ca2+ or Mn2+ could replace Mg2+ to a certain, though small, extent. Apparent KM values with respect to PIP and ATP were 10 and 65 microM, respectively. GTP was slightly utilized by the kinase as phosphate donor while CTP was not. Quercetin inhibited the enzyme with Ki = 34 microM. Extending our previous observations (Urumow, T. and Wieland, O.H. (1986) FEBS Lett. 207, 253-257 and Urumow, T. and Wieland, O.H. (1988) Biochim. Biophys. Acta 972, 232-238) [gamma S]pppG still stimulated the PIP kinase in extracts of solubilized liver membranes. 20-40% (NH4)2SO4 precipitation of the membrane extracts yielded a fraction that contained the bulk of enzyme activity but did not respond to stimulation by [gamma S]pppG any longer. This was restored by recombination with a protein fraction collected at 40-70% (NH4)2SO4 saturation, presumably containing a GTP binding protein and/or some other factor separated from the PIP kinase. In the reconstituted system [gamma S]pppG stimulated PIP kinase in a concentration dependent manner with maximal activation at 5 microM. This effect was not mimicked by [gamma S]pppA and was blocked by [beta S]ppG. These results strongly support our view that in liver membranes PIP kinase is regulated by a G-protein.
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PMID:Purification and partial characterization of phosphatidylinositol-4-phosphate kinase from rat liver plasma membranes. Further evidence for a stimulatory G-protein. 215 97

Incorporation of 32P from [gamma-32P]ATP into phosphatidylinositol 4,5-bisphosphate (PIP2) in membranes isolated from rat brain was enhanced in a concentration-dependent manner by the GTP analogue guanosine 5'-O-(thio)triphosphate (GTP gamma S). In contrast, neither the labeling of phosphatidylinositol 4-phosphate in the same membranes nor PIP kinase activity in the soluble fraction were stimulated by GTP gamma S. Synthesis of [32P]PIP2 was not stimulated by GTP, GDP, GMP, or ATP; however, the stimulatory effects of GTP gamma S were antagonized by GTP, GDP, and guanosine 5'-O-thiodiphosphate (GDP beta S). The nucleotide-stimulated labeling of PIP2 was not due to protection of [gamma-32P] ATP from hydrolysis, activation of PIP2 hydrolysis by phospholipase C, or inhibition of PIP2 hydrolysis by its phosphomonoesterase. Therefore, phosphatidylinositol 4-phosphate kinase activity in brain membranes may be regulated by a guanine nucleotide regulatory protein. This system may enhance the resynthesis of PIP2 following receptor-mediated activation of phospholipase C.
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PMID:Regulation of brain phosphatidylinositol-4-phosphate kinase by GTP analogues. A potential role for guanine nucleotide regulatory proteins. 253 38

To investigate the modulation of phosphatidylinositol 4-phosphate kinase activity by the degree of phosphorylation of the B-50 protein, the enzyme was purified from rat brain cytosol by ammonium sulphate precipitation and DEAE-cellulose column chromatography. Purified rat brain B-50 was phosphorylated with protein kinase C and dephosphorylated with alkaline phosphatase. Incubation of the semi-purified phosphatidylinositol 4-phosphate kinase with 1 microgram of the B-50 preparation enriched in the dephospho-form, resulted in a small reduction of phosphatidylinositol 4-phosphate kinase activity (-16%), whereas incubation with the phospho B-50 preparation inhibited the enzyme activity by 40%. The effect of exogenous B-50 was studied in the presence of 10 micrograms albumin to minimize aspecific protein-protein interactions. The present data on the effect of exogenous B-50 protein on phosphatidylinositol 4-phosphate kinase activity, further support our hypothesis that the phosphorylation state of B-50 may be a regulatory factor in phosphoinositide metabolism in rat brain.
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PMID:Modulation of the activity of purified phosphatidylinositol 4-phosphate kinase by phosphorylated and dephosphorylated B-50 protein. 298 32