Document Detail

Kinetic independence of the subunits of cytosolic glutathione transferase from the rat.
MedLine Citation:
PMID:  4062896     Owner:  NLM     Status:  MEDLINE    
The steady-state kinetics of the dimeric glutathione transferases deviate from Michaelis-Menten kinetics, but have hyperbolic binding isotherms for substrates and products of the enzymic reaction. The possibility of subunit interactions during catalysis as an explanation for the rate behaviour was investigated by use of rat isoenzymes composed of subunits 1, 2, 3 and 4, which have distinct substrate specificities. The kinetic parameter kcat./Km was determined with 1-chloro-2,4-dinitrobenzene, 4-hydroxyalk-2-enals, ethacrynic acid and trans-4-phenylbut-3-en-2-one as electrophilic substrates for six isoenzymes: rat glutathione transferases 1-1, 1-2, 2-2, 3-3, 3-4 and 4-4. It was found that the kcat./Km values for the heterodimeric transferases 1-2 and 3-4 could be predicted from the kcat./Km values of the corresponding homodimers. Likewise, the initial velocities determined with transferases 3-3, 3-4 and 4-4 at different degrees of saturation with glutathione and 1-chloro-2,4-dinitrobenzene demonstrated that the kinetic properties of the subunits are additive. These results show that the subunits of glutathione transferase are kinetically independent.
U H Danielson; B Mannervik
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Biochemical journal     Volume:  231     ISSN:  0264-6021     ISO Abbreviation:  Biochem. J.     Publication Date:  1985 Oct 
Date Detail:
Created Date:  1985-12-19     Completed Date:  1985-12-19     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2984726R     Medline TA:  Biochem J     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  263-7     Citation Subset:  IM    
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MeSH Terms
Binding Sites
Cytosol / enzymology
Glutathione Transferase / metabolism*
Isoenzymes / metabolism*
Liver / enzymology*
Models, Biological
Substrate Specificity
Reg. No./Substance:
0/Isoenzymes; EC Transferase

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