Document Detail


Novel pyrophosphate-forming acetate kinase from the protist Entamoeba histolytica.
MedLine Citation:
PMID:  22903977     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Acetate kinase (ACK) catalyzes the reversible synthesis of acetyl phosphate by transfer of the γ-phosphate of ATP to acetate. Here we report the first biochemical and kinetic characterization of a eukaryotic ACK, that from the protist Entamoeba histolytica. Our characterization revealed that this protist ACK is the only known member of the ASKHA structural superfamily, which includes acetate kinase, hexokinase, and other sugar kinases, to utilize inorganic pyrophosphate (PP(i))/inorganic phosphate (P(i)) as the sole phosphoryl donor/acceptor. Detection of ACK activity in E. histolytica cell extracts in the direction of acetate/PP(i) formation but not in the direction of acetyl phosphate/P(i) formation suggests that the physiological direction of the reaction is toward acetate/PP(i) production. Kinetic parameters determined for each direction of the reaction are consistent with this observation. The E. histolytica PP(i)-forming ACK follows a sequential mechanism, supporting a direct in-line phosphoryl transfer mechanism as previously reported for the well-characterized Methanosarcina thermophila ATP-dependent ACK. Characterizations of enzyme variants altered in the putative acetate/acetyl phosphate binding pocket suggested that acetyl phosphate binding is not mediated solely through a hydrophobic interaction but also through the phosphoryl group, as for the M. thermophila ACK. However, there are key differences in the roles of certain active site residues between the two enzymes. The absence of known ACK partner enzymes raises the possibility that ACK is part of a novel pathway in Entamoeba.
Authors:
Matthew L Fowler; Cheryl Ingram-Smith; Kerry S Smith
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2012-08-17
Journal Detail:
Title:  Eukaryotic cell     Volume:  11     ISSN:  1535-9786     ISO Abbreviation:  Eukaryotic Cell     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-02     Completed Date:  2013-02-21     Revised Date:  2013-07-12    
Medline Journal Info:
Nlm Unique ID:  101130731     Medline TA:  Eukaryot Cell     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1249-56     Citation Subset:  IM    
Affiliation:
Department of Genetics and Biochemistry, Clemson University, Clemson, South Carolina, USA.
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MeSH Terms
Descriptor/Qualifier:
Amino Acid Sequence
Binding Sites
Catalytic Domain
Diphosphates / metabolism*
Entamoeba histolytica / enzymology*,  genetics
Molecular Sequence Data
Organophosphates / metabolism
Phosphotransferases (Carboxyl Group Acceptor) / chemistry,  genetics,  metabolism*
Protozoan Proteins / chemistry,  genetics,  metabolism*
Chemical
Reg. No./Substance:
0/Diphosphates; 0/Organophosphates; 0/Protozoan Proteins; 4E862E7GRQ/diphosphoric acid; 590-54-5/acetyl phosphate; EC 2.7.2.-/Phosphotransferases (Carboxyl Group Acceptor); EC 2.7.2.12/acetate kinase(pyrophosphate)
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