Reactivities of the sulphydryl groups of horse (Equus caballus) haemoglobin (1013.11)
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Abstract
Description
The kinetics of the reaction of Ellman’s reagent (DTNB) with CysF9[93]5 sulphydryl
group of the horse haemoglobins were studied at neutral and physiological pH
(6.8 < pH > 7.6) ranges under pseudo first order conditions. The reaction is of
first order with respect to the DTNB concentration. The reactions are pH
dependent of the observed rate constant gave a complex trend. The observed rate
shows that at neutral pH, the presence of inositol hexakisphosphate (inositol-P
6
)
increases the pseudo first order rate constant. For the first time, inositol-P
6
increases rate of forward reaction, kF at neutral pH values by increasing the mean
value of the transition constant, K
rt3
. The K
rt3
for the haemoglobin without
inositol-P
6
gave the value of 0.138 ± 0.1 while the haemoglobin in the presence of
inositol-P
6
gave the K
rt3
value of 0.325 ± 0.2. The results show that inositol-P
6
increases the relative population of the t tertiary conformation. So, it increases the
reactivity of CysF9[93]5 by changing the relative distribution of two protein
conformations
Keywords
QH301 Biology