Jonathan Oyebamiji Babalola, Najeem Abiola Adesola Babarinde, Idowu Abideen Adeogun and Titilola Stella Akingbola
Keywords: Haemoglobin C, Sulphyldryl group, Ionizable groups; Inositol-P6; Ionic strength.
Abstract: The pH dependence of the second order rate constant of the reaction of 5,5’-dithiobis(2-nitrobenzoate) (DTNB) with CysF9[93]? sulphydryl group of the oxy and carbonmonoxy derivatives of stripped haemoglobin C are complex while that of aquomet haemoglobins resembles the titration curve of a diprotic acid. However, in the presence of inositol hexakisphosphate, the profiles of oxy and carbomonoxy derivatives become simple while that of aquomet becomes bowl shaped. Increased ionic strength also simplified the complex profile. The pQs of the ionizable groups linked to the reactivity of DTNB with CysF9[93]? sulphydryl group range between 5.6 and 8.7 in stripped haemoglobin. The presence of inositol-P6 decreases the pQ values to the range of 4.3 and 8.4. When compared with haemoglobins A and S, the reaction rate of heamoglobin C is lower than haemoglobin A but faster than haemoglobin S, implying that the net charge on the molecule has no direct relationship with the reaction rates.
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