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.
Download full-text PDF |
Source |
|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1149311 | PMC |
| http://dx.doi.org/10.1042/bj2530387 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Effect of exogenous phytase on degradation of inositol phosphate in dairy cows.
J Dairy Sci
March 2013
Department of Animal Science, Faculty of Science and Technology, Aarhus University, AU Foulum, PO Box 50, 8830 Tjele, Denmark.
The effect of exogenous phytase on inositol phosphate degradation in the rumen of dairy cows was investigated in a 4 × 4 Latin square design. Four lactating Danish Holstein cows fitted with ruminal, duodenal, and ileal cannulas were offered a total mixed ration (TMR) with a high content of inositol phosphate and supplemented with 1 of 4 concentrations of phytase [none, low, medium, or high, corresponding to 23, 2,023, 3,982, and 6,015 phytase units/kg of dry matter (DM)]. Exogenous phytase lead to a higher rumen pool of phytase.
View Article and Find Full Text PDFONIOM (DFT:MM) study of the catalytic mechanism of myo-inositol monophosphatase: essential role of water in enzyme catalysis in the two-metal mechanism.
J Phys Chem B
January 2013
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
myo-Inositol monophosphatase (IMPase), a putative target of lithium therapy for bipolar disorder, is an enzyme that catalyzes the hydrolysis of myo-inositol-1-phosphate (Ins(1)P) into myo-inositol (MI) and inorganic phosphate. It is known that either two or three Mg(2+) ions are used as cofactors in IMPase catalysis; however, the detailed catalytic mechanism and the specific number of Mg(2+) ions required have long remained obscure. To obtain a clearer view of the IMPase reaction, we undertook extensive ONIOM hybrid quantum mechanics and molecular mechanics (QM/MM) calculations, to evaluate the reaction with either three or two Mg(2+) ions.
View Article and Find Full Text PDFCrystal structure of Staphylococcal dual specific inositol monophosphatase/NADP(H) phosphatase (SAS2203) delineates the molecular basis of substrate specificity.
Biochimie
March 2012
Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India.
Inositol monophosphatase (IMPase) family of proteins are Mg(2+) activated Li(+) inhibited class of ubiquitous enzymes with promiscuous substrate specificity. Herein, the molecular basis of IMPase substrate specificity is delineated by comparative crystal structural analysis of a Staphylococcal dual specific IMPase/NADP(H) phosphatase (SaIMPase - I) with other IMPases of different substrate compatibility, empowered by in silico docking and Escherichia coli SuhB mutagenesis analysis. Unlike its eubacterial and eukaryotic NADP(H) non-hydrolyzing counterparts, the composite structure of SaIMPase - I active site pocket exhibits high structural resemblance with archaeal NADP(H) hydrolyzing dual specific IMPase/FBPase.
View Article and Find Full Text PDFIn silico study on the substrate binding manner in human myo-inositol monophosphatase 2.
J Mol Model
October 2011
Department of Bioinformatics, College of Information Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
The human IMPA2 gene encoding myo-inositol monophosphatase 2 is highly implicated with bipolar disorder but the substrates and the reaction mechanism of myo-inositol monophosphatase 2 have not been well elucidated.9 In the present study, we constructed 3D models of three- and two-Mg(2+)-ion bound myo-inositol monophosphatase 2, and studied substrate-binding manners using the docking program AutoDock3. The subsequent study showed that the three-metal-ion model could interact with myo-inositol monophosphates, as follows: The phosphate moiety coordinated three Mg(2+) ions, and the inositol ring formed hydrogen bonds with the amino acids conserved in the family.
View Article and Find Full Text PDFHigh-resolution structure of myo-inositol monophosphatase, the putative target of lithium therapy.
Acta Crystallogr D Biol Crystallogr
May 2005
Biomolecular Sciences Group, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, England.
Inositol monophosphatase is a key enzyme of the phosphatidylinositol signalling pathway and the putative target of the mood-stabilizing drug lithium. The crystal structure of bovine inositol monophosphatase has been determined at 1.4 A resolution in complex with the physiological magnesium ion ligands.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!