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

A specific soluble inositol phosphate 5-phosphomonoesterase has been purified approximately 2,700-fold from a 120,000g supernatant of rabbit neutrophil homogenate. The specific enzyme represented 25-50% of the total hydrolytic activity toward inositol, 1,4,5-trisphosphate (Ins-1,4,5-P3) with the remaining activity hydrolyzing both Ins-1,4,5-P3 as well as inositol 1,4-bisphosphate (Ins-1,4-P2). However, the enzyme could not be identified on sodium dodecyl sulfate-polyacrylamide gels stained with Coomassie blue, indicating that it represents a minor protein in the purified enzyme preparations. The purified enzyme has an apparent molecular mass of 43,000-47,000 daltons as determined by gel filtration and is free of other inositol phosphate phosphomonoesterases. The enzyme hydrolyzes Ins-1,4,5-P3 with an apparent Km of 18 microM and a Vmax of 1.2 mumol/min/mg. The 5-phosphomonoesterase requires Mg2+ for activity and is not affected by physiological concentrations of Ca2+ or calmodulin. The pH optimum for activity is 7.5. Inositol 1,3,4,5-tetrakisphosphate is a potent competitive inhibitor of Ins-1,4,5-P3 hydrolysis (Ki = microM), whereas Ins-1,4-P2 is a weak inhibitor (Ki = 173 microM). Ins-1,4,5-P3 hydrolysis is relatively unaffected by monophosphorylated substrates, however, bisphosphorylated substrates are potent inhibitors. Comparisons of neutrophil 5-phosphomonoesterase characteristics with those of platelet and rat brain enzymes support the idea that each 5-phosphomonoesterase may be a unique enzyme and play a different role dependent upon the cell or tissue in which it acts.
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PMID:Purification and characterization of soluble inositol 1,4,5-trisphosphate 5-phosphomonoesterase from rabbit peritoneal neutrophils. 216 94

Two soluble forms of inositol phosphate 5-phosphomonoesterase have been partially purified and characterized from rat brain and are referred to as type 1 and type 2 according to their order of elution from DEAE-Sepharose. Together, these enzymes represent 26 +/- 3% (mean +/- S.E., n = 4) of the total inositol 1,4,5-triphosphate (Ins(1,4,5)P3) phosphatase activity assayed in crude brain homogenate and are present in approximately equal total activities in a 100,000 x g supernatant, with the remainder being membrane-bound. Both soluble enzymes require Mg2+ for activity, are moderately inhibited by Ca2+ in the micromolar range, and can be inhibited by millimolar concentrations of a variety of phosphorylated compounds. The type 1 enzyme has been purified to a specific activity of 1.06 mumol/min/mg protein. It elutes as a 60-kDa protein on Sephacryl S-200. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the type 1 enzyme correlates with a pair of protein bands of 66 and 60 kDa. It has apparent Km values of 3 and 0.8 microM for Ins(1,4,5)P3 and inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), respectively, and hydrolyses Ins(1,4,5)P3 approximately 12 times faster than Ins(1,3,4,5)P4. The type 2 enzyme has been purified to a specific activity of 15.2 mumol/min/mg protein, elutes as a protein of 160 kDa on Sephacryl S-300, and migrates as a similarly sized subunit on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It has an apparent Km for Ins(1,4,5)P3 of 18 microM. Its apparent Km for Ins(1,3,4,5)P4, however, is greater than 150 microM, suggesting that this enzyme is primarily an Ins(1,4,5)P3 5-phosphomonoesterase. The relationship of these two enzymes to the inositol tris/tetrakisphosphate pathway is discussed.
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PMID:Purification and characterization of two types of soluble inositol phosphate 5-phosphomonoesterases from rat brain. 282 17

Rabbit peritoneal neutrophils, permeabilized with Triton X-100, contain inositol phosphate 5-phosphomonoesterase activity capable of converting [3H]inositol 1,4,5-trisphosphate (Ins-1,4,5-P3) to [3H]inositol 1,4-bisphosphate. This activity is found predominantly associated with the soluble component of fractionated neutrophils. It is comprised of specific and nonspecific activities toward Ins-1,4,5-P3 which can be separated by cation exchange chromatography. Treatment of neutrophils with phorbol 12-myristate 13-acetate (PMA) prior to permeabilization does not affect the rate of Ins-1,4,5-P3 breakdown by these cells. In addition, activation of endogenous protein kinase C in a soluble fraction prepared from neutrophils does not affect the specific inositol phosphate 5-phosphomonoesterase activity of this fraction. Taken together, these results provide evidence that activation of protein kinase C in the neutrophil does not affect its 5-phosphomonoesterase activity. Unlike platelets, the phosphorylation of a 5-phosphomonoesterase, if it occurs, may not play a role in the inhibitory effects of PMA on neutrophil responsiveness.
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PMID:Demonstration of inositol phosphate 5-phosphomonoesterase activity in rabbit neutrophils: absence of a role for protein kinase C. 284 77

D-myo-Inositol 1,4,5-trisphosphate has been previously demonstrated to act as a second messenger for the hormonal mobilization of intracellular calcium in rat liver. In this study, the breakdown of D-myo-inositol 1,4,5-trisphosphate by a phosphatase activity was characterized. Using partially purified subcellular fractions, it was found that D-myo-inositol 1,4,5-trisphosphate phosphatase (I-P3ase) specific activity was highest in the plasma membrane fraction, while D-myo-inositol 1,4-bisphosphate phosphatase specific activity was highest in the cytosolic and microsomal fractions. The plasma membrane I-P3ase was Mg2+-dependent with optimal activity observed at 0.5-1.5 mM free Mg2+. The enzyme had a neutral pH optimum, suggesting that it was neither an acid nor alkaline phosphatase. Neither LiCl nor NaF inhibited the I-P3ase activity. However, both L-cysteine and dithiothreitol stimulated the activity 2-fold. Spermine (2.0 mM) inhibited the I-P3ase activity by 50%, while putrescine and spermidine had little or no effect.
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PMID:Characterization of D-myo-inositol 1,4,5-trisphosphate phosphatase in rat liver plasma membranes. 609 66