Document Detail

Reaction mechanism of phosphoenolpyruvate carboxylase. Bicarbonate-dependent dephosphorylation of phosphoenol-alpha-ketobutyrate.
MedLine Citation:
PMID:  6326809     Owner:  NLM     Status:  MEDLINE    
Phosphoenolpyruvate carboxylase (EC of Escherichia coli was found to catalyze the cleavage reaction of phosphoenol-alpha-ketobutyrate, a potent competitive inhibitor with the substrate, to yield inorganic phosphate and alpha-ketobutyrate. The rate of phosphate liberation was about 1/20 th of that in the normal reaction with phosphoenolpyruvate. Although HCO3- and Mg2+ were the necessary components in this reaction as in the normal reaction, no CO2 fixation could be detected. When the reaction was carried out in the presence of [18O]HCO3-, multiple incorporations of 18O atoms into the liberated phosphate molecule were observed. The molar proportions of phosphate having one, two, and three 18O atoms were 70, 25, and 5%, respectively. No multiple but only one 18O atom incorporation was observed when phosphoenolpyruvate was used as a substrate. These results suggest that the liberation of phosphate can proceed without CO2 fixation, being not consistent with the concerted mechanism [ Maruyama , H., Easterday , R. L., Chang, H. C., & Lane, M. D. (1966) J. Biol. Chem. 241, 2405-2412] but essentially consistent with the current stepwise mechanism [O'Leary, M. H., Rife , J. E., & Slater , J. D. (1981) Biochemistry 20, 7308-7314].
N Fujita; K Izui; T Nishino; H Katsuki
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochemistry     Volume:  23     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  1984 Apr 
Date Detail:
Created Date:  1984-07-20     Completed Date:  1984-07-20     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1774-9     Citation Subset:  IM    
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MeSH Terms
Bicarbonates / pharmacology*
Carboxy-Lyases / metabolism*
Escherichia coli / enzymology*
Mass Spectrometry
Phosphates / analysis
Phosphoenolpyruvate / analogs & derivatives*,  metabolism
Phosphoenolpyruvate Carboxylase / isolation & purification,  metabolism*
Substrate Specificity
Reg. No./Substance:
0/Bicarbonates; 0/Phosphates; 25956-55-2/phosphoenol-2-ketobutyrate; 73-89-2/Phosphoenolpyruvate; EC 4.1.1.-/Carboxy-Lyases; EC Carboxylase

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