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Purification and properties of myo-inositol-1-phosphatase from bovine brain.

ABSTRACT: myo-Inositol-1-phosphatase from bovine brain was purified over 2000-fold. The native enzyme has a Mr of 59,000, and on SDS/polyacrylamide-gel electrophoresis the subunit Mr was 31,000. Thus the native enzyme is a dimer of two apparently identical subunits. The enzyme, purified to a specific activity of more than 300 units/mg of protein (1 unit of enzyme activity corresponds to the release of 1 mumol of Pi/h at 37 degrees C), catalysed the hydrolysis of a variety of phosphorylated compounds, the best one, in terms of V/Km, being D-myo-inositol 1-phosphate. Kinetic constants of compounds tested, including both isomers of glycerophosphate and two deoxy forms of beta-glycerophosphate, were measured. They show the importance of the two hydroxyl groups which are adjacent to the phosphate in myo-inositol 1-phosphate. With a wide variety of substrates Li+ was found to be an uncompetitive inhibitor whose Ki varied with substrate structure.

SUBMITTER: Attwood PV

PROVIDER: S-EPMC1149311 | biostudies-other | 1988 Jul

REPOSITORIES: biostudies-other

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The purification and properties of myo-inositol monophosphatase from bovine brain.

Project description:1. An inositol monophosphatase was purified to homogeneity from bovine brain. 2. The enzyme is a dimer of subunit Mr 29,000. 3. The enzyme hydrolyses both enantiomers of myo-inositol 1-phosphate and both enantiomers of myo-inositol 4-phosphate, but has no activity towards inositol bisphosphates, inositol trisphosphates or inositol 1,3,4,5-tetrakisphosphate. 4. Several non-inositol-containing monophosphates are also substrates. 5. The enzyme requires Mg2+ for activity, and Zn2+ supports activity to a small extent. 6. Other bivalent cations (including Zn2+) are inhibitors, competitive with Mg2+. 7. Phosphate, but not inositol, is an inhibitor competitive with substrate. 8. Li+ inhibits hydrolysis of inositol 1-phosphate and inositol 4-phosphate uncompetitively with different apparent Ki values (1.0 mM and 0.26 mM respectively).

| S-EPMC1148789 | biostudies-other

Purification and properties of inositol-1,4-bisphosphatase from bovine brain.

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| S-EPMC1149370 | biostudies-other

Purification, crystallization and preliminary crystallographic analysis of mouse myo-inositol oxygenase.

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myo-Inositol phosphorothioates, phosphatase-resistant analogues of myo-inositol phosphates. Synthesis of DL-myo-inositol 1,4-bisphosphate and DL-myo-inositol 1,4-bisphosphorothioate.

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Effects of myo-inositol plus alpha-lactalbumin in myo-inositol-resistant PCOS women.

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Kinetic and structural analysis of a bacterial protein tyrosine phosphatase-like myo-inositol polyphosphatase.

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Identification of a mammalian H(+)-myo-inositol symporter expressed predominantly in the brain.

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Neurometabolite mapping highlights elevated myo-inositol profiles within the developing brain in down syndrome.

Project description:The neurodevelopmental phenotype in Down Syndrome (DS), or Trisomy 21, is variable including a wide spectrum of cognitive impairment and a high risk of early-onset Alzheimer's disease (AD). A key metabolite of interest within the brain in DS is Myo-inositol (mIns). The NA+/mIns co-transporter is located on human chromosome 21 and is overexpressed in DS. In adults with DS, elevated brain mIns was previously associated with cognitive impairment and proposed as a risk marker for progression to AD. However, it is unknown if brain mIns is increased earlier in development. The aim of this study was to estimate mIns concentration levels and key brain metabolites [N-acetylaspartate (NAA), Choline (Cho) and Creatine (Cr)] in the developing brain in DS and aged-matched controls. We used in vivo magnetic resonance spectroscopy (MRS) in neonates with DS (n = 12) and age-matched controls (n = 26) scanned just after birth (36-45 weeks postmenstrual age). Moreover, we used Mass Spectrometry in early (10-20 weeks post conception) ex vivo fetal brain tissue samples from DS (n = 14) and control (n = 30) cases. Relative to [Cho] and [Cr], we report elevated ratios of [mIns] in vivo in the basal ganglia/thalamus, in neonates with DS, when compared to age-matched typically developing controls. Glycine concentration ratios [Gly]/[Cr] and [Cho]/[Cr] also appear elevated. We observed elevated [mIns] in the ex vivo fetal cortical brain tissue in DS compared with controls. In conclusion, a higher level of brain mIns was evident as early as 10 weeks post conception and was measurable in vivo from 36 weeks post-menstrual age. Future work will determine if this early difference in metabolites is linked to cognitive outcomes in childhood or has utility as a potential treatment biomarker for early intervention.

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D-myo-inositol 1,4,5-trisphosphate phosphatase in skeletal muscle.

Project description:The presence and subcellular distribution of D-myo-inositol 1,4,5-trisphosphate phosphatase (InsP3ase) in rabbit fast-twitch skeletal muscle were investigated. A specific InsP3ase was found in both sarcotubular-membrane and soluble fractions. Membrane-bound InsP3ase accounted for 60-65% of total activity. The InsP3ase was detected both on the surface membranes and on the InsP3-sensitive intracellular Ca2+ store, i.e. the sarcoplasmic reticulum. The Km for inositol 1,4,5-trisphosphate (InsP3) ranged between 15 and 18 microM, and the highest Vmax. (19.6 nmol of InsP3 hydrolysed/min per mg of protein) was measured in a membrane fraction enriched in transverse tubules. Several known inhibitors of InsP3ase, e.g. 2,3-bisphosphoglycerate, CdCl2 and EDTA, were active on skeletal-muscle InsP3ase. Total InsP3ase activity of both rabbit and frog skeletal muscle was comparable with that of rabbit brain, liver and main pulmonary artery (smooth muscle). The present results are consistent with the hypothesis that InsP3 plays a role in excitation-contraction coupling in skeletal muscle [Volpe, Salviati, Di Virgilio & Pozzan (1985) Nature (London) 316, 347-349].

| S-EPMC1135109 | biostudies-other

Myo-inositol reduces ?-catenin activation in colitis.

Project description:AIM:To assess dietary myo-inositol in reducing stem cell activation in colitis, and validate p?-cateninS552 as a biomarker of recurrent dysplasia. METHODS:We examined the effects of dietary myo-inositol treatment on inflammation, p?-cateninS552 and pAkt levels by histology and western blot in IL-10-/- and dextran sodium sulfate-treated colitic mice. Additionally, we assessed nuclear p?-cateninS552 in patients treated with myo-inositol in a clinical trial, and in patients with and without a history of colitis-induced dysplasia. RESULTS:In mice, p?-cateninS552 staining faithfully reported the effects of myo-inositol in reducing inflammation and intestinal stem cell activation. In a pilot clinical trial of myo-inositol administration in patients with a history of low grade dysplasia (LGD), two patients had reduced numbers of intestinal stem cell activation compared to the placebo control patient. In humans, p?-cateninS552 staining discriminated ulcerative colitis patients with a history of LGD from those with benign disease. CONCLUSION:Enumerating crypts with increased numbers of p?-cateninS552 - positive cells can be utilized as a biomarker in colitis-associated cancer chemoprevention trials.

| S-EPMC5537179 | biostudies-literature

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