Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 2 de 2
Filter
Add filters








Language
Year range
1.
Indian J Biochem Biophys ; 1991 Feb; 28(1): 16-21
Article in English | IMSEAR | ID: sea-28733

ABSTRACT

Kinetics of thermal inactivation of apo-glyceraldehyde 3-phosphate dehydrogenase have been investigated under various conditions. At most pH values, the loss of enzyme activity takes place in two phases, a fast and a slow phase. The data correspond to the rate equation A = Afast.e-kfast.t + Aslow.e-kslow, where A is the observed residual activity (expressed as % of initial activity) at time t, Afast and Aslow are amplitudes (expressed as % of initial activity, so that Afast + Aslow = 100) and kfast and kslow the rate constants of the fast and slow phases, respectively. At pH 9 or below, Afast = Aslow = 50%. As pH is increased above 9, Afast increases gradually till at pH 10 or above when it accounts for the entire initial activity (single exponential decay). The rate constants of the two phases are strongly affected by the nature of the buffer, temperature and pH, but the amplitudes depend on pH alone. It has been suggested that the tetrameric enzyme exists in two conformations of different molecular symmetry, namely C2 (two pairs of sites of unequal stability, predominating at pH 9 or below) and D2 symmetry (four equivalent sites, predominating at pH 10 or above). The C2 in equilibrium D2 transformation is found to be highly cooperative with midpoint at pH 9.6.


Subject(s)
Animals , Apoenzymes/metabolism , Biological Evolution , Glyceraldehyde-3-Phosphate Dehydrogenases/chemistry , Hydrogen-Ion Concentration , Kinetics , Macromolecular Substances , Muscles/enzymology , Rabbits , Temperature
SELECTION OF CITATIONS
SEARCH DETAIL