Document Detail


Oxidation of the diphosphoinositol polyphosphate phosphohydrolase-like Nudix hydrolase Aps from Drosophila melanogaster induces thermolability--A possible regulatory switch?
MedLine Citation:
PMID:  20394834     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Unlike mammalian cells, Drosophila melanogaster contains only a single member of the diphosphoinositol polyphosphate phosphohydrolase subfamily of the Nudix hydrolases, suggesting that functional specialisation has not occurred in this organism. In order to evaluate its function, Aps was cloned and characterized. It hydrolyses a range of (di)nucleoside polyphosphates, the most efficient being guanosine 5'-tetraphosphate (K(m)=11 microM, k(cat)=0.79 s(-1)). However, it shows a 5-fold preference for the hydrolysis of diphosphoinositol pentakisphosphate (PP-InsP(5), K(m)=0.07 microM, k(cat)=0.024 s(-1)). Assayed at 26 degrees C, Aps had an alkaline pH optimum and required a divalent ion: Mg(2+) (10-20 mM) or Mn(2+) (1 mM) were preferred for nucleotide hydrolysis and Mg(2+) (0.5-1 mM) or Co(2+) (1-100 microM) for PP-InsP(5) hydrolysis. GFP-fusions showed that Aps was predominantly cytoplasmic, with some nuclear localization. In the absence of dithiothreitol Aps was heat labile, rapidly losing activity even at 36 degrees C, while in the presence of dithiothreitol, Aps was heat stable, surviving for 5 min at 76 degrees C. Heat lability was restored by H(2)O(2) and mass spectrometric analysis suggested that this was due to reversible dimerisation involving two inter-molecular disulphides between Cys23 and Cys25. Aps expression was highest in embryos and declined throughout development. The ratio of PP-InsP(5) to inositol hexakisphosphate also decreased throughout development, with the highest level of PP-InsP(5) found in embryos. These data suggest that the redox state of Aps may play a role in controlling its activity by altering its stability, something that could be important for regulating PP-InsP(5) during development.
Authors:
Lucinda Winward; William G F Whitfield; Alexander G McLennan; Stephen T Safrany
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-04-13
Journal Detail:
Title:  The international journal of biochemistry & cell biology     Volume:  42     ISSN:  1878-5875     ISO Abbreviation:  Int. J. Biochem. Cell Biol.     Publication Date:  2010 Jul 
Date Detail:
Created Date:  2010-06-02     Completed Date:  2010-09-27     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9508482     Medline TA:  Int J Biochem Cell Biol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  1174-81     Citation Subset:  IM    
Copyright Information:
Copyright 2010 Elsevier Ltd. All rights reserved.
Affiliation:
Division of Cell Signalling, University of Dundee, Dow Street, Dundee DD1 4HN, United Kingdom. lusi83@hotmail.com
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MeSH Terms
Descriptor/Qualifier:
Acid Anhydride Hydrolases / chemistry,  genetics,  metabolism*
Adenine Nucleotides / metabolism
Amino Acid Sequence
Animals
Cations, Divalent / pharmacology
Chromatography, High Pressure Liquid
Dithiothreitol / pharmacology
Drosophila Proteins / chemistry,  genetics,  metabolism*
Drosophila melanogaster / enzymology*,  genetics
Enzyme Stability / drug effects
Gene Expression Regulation, Developmental / drug effects
Hydrogen-Ion Concentration / drug effects
Hydrolysis / drug effects
Inositol Phosphates / metabolism
Kinetics
Molecular Sequence Data
Oxidation-Reduction / drug effects
Protein Transport / drug effects
Pyrophosphatases / chemistry,  genetics,  metabolism*
Sequence Alignment
Subcellular Fractions / drug effects,  enzymology
Substrate Specificity / drug effects
Temperature*
Grant Support
ID/Acronym/Agency:
//Biotechnology and Biological Sciences Research Council
Chemical
Reg. No./Substance:
0/Adenine Nucleotides; 0/Cations, Divalent; 0/Drosophila Proteins; 0/Inositol Phosphates; 148077-18-3/1-diphosphoinositol pentakisphosphate; 3483-12-3/Dithiothreitol; EC 3.6.-/Acid Anhydride Hydrolases; EC 3.6.1.-/Aps protein, Drosophila; EC 3.6.1.-/Pyrophosphatases; EC 3.6.1.-/diphosphoinositol polyphosphate phosphohydrolase; EC 3.6.1.-/nudix hydrolases

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