Document Detail


In vitro synthesis of colominic acid by membrane-bound sialyltransferase of Escherichia coli K-235. Kinetic properties of this enzyme and inhibition by CMP and other cytidine nucleotides.
MedLine Citation:
PMID:  2643517     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The membrane-bound sialyltransferase obtained from Escherichia coli K-235 grown in a chemically defined medium (ideal for colominic acid production) was studied. The in vivo half-life calculated for this enzyme was 20 h. Kinetic tests revealed (at 33 degrees C and pH 8.3) hyperbolic behaviour with respect to CMP-Neu5Ac (Km250 microM) and a transition temperature at 31.3 degrees C. The enzyme was inhibited by NH4+, some divalent cations and by several agents that react with thiol groups. Detergents and fatty acids also inhibited the sialyltransferase activity. In vitro synthesis of colominic acid is strongly inhibited by CMP by blocking the incorporation of [14C]Neu5Ac into a protein-complex intermediate and therefore into free polymer. CDP and CTP also inhibited (91% and 84%) this enzyme activity whereas cytosine and cytidine had no effect. CMP inhibition corresponded to a competitive model the calculated Ki was 30 microM. Incubations of protein[14C]Neu5Ac with CMP, CDP and CTP led to de novo synthesis of CMP-[14C]Neu5Ac. The presence of colominic acid, which usually displaces the reaction equilibrium towards polymer synthesis, did not affect this de novo CMP-[14C]Neu5Ac formation. CMP also inhibited in vivo colominic acid biosynthesis.
Authors:
A I Ortiz; A Reglero; L B Rodríguez-Aparicio; J M Luengo
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  European journal of biochemistry / FEBS     Volume:  178     ISSN:  0014-2956     ISO Abbreviation:  Eur. J. Biochem.     Publication Date:  1989 Jan 
Date Detail:
Created Date:  1989-03-02     Completed Date:  1989-03-02     Revised Date:  2007-07-23    
Medline Journal Info:
Nlm Unique ID:  0107600     Medline TA:  Eur J Biochem     Country:  GERMANY, WEST    
Other Details:
Languages:  eng     Pagination:  741-9     Citation Subset:  IM    
Affiliation:
Departamento de Bioquímica y Biología Molecular, Universidad de León, Spain.
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MeSH Terms
Descriptor/Qualifier:
Cell Membrane / enzymology
Cytidine Monophosphate / pharmacology*
Cytidine Triphosphate / pharmacology
Cytosine Nucleotides / pharmacology*
Detergents / pharmacology
Escherichia coli / enzymology*
Fatty Acids, Nonesterified / pharmacology
Kinetics
Polysaccharides / biosynthesis*
Sialyltransferases / antagonists & inhibitors,  metabolism*
Thermodynamics
Chemical
Reg. No./Substance:
0/Cytosine Nucleotides; 0/Detergents; 0/Fatty Acids, Nonesterified; 0/Polysaccharides; 63-37-6/Cytidine Monophosphate; 65-47-4/Cytidine Triphosphate; 9013-15-4/colominic acid; EC 2.4.99.-/Sialyltransferases

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