Kinetic and Thermodynamic Studies on Afp Binding to Afp Antibody in Colorectal Tumor Homogenates

• Published in: Science journal of University of Zakho (Online) Vol. 1; no. 2; pp. 699 - 714
• Main Authors: Bilal J. M. Al Rawi, Sami A. Al Mudhaffar, Hathama R. Hassan
• Format: Journal Article
• Language: English
• Published: University of Zakho 01.09.2013
• Subjects: The
• ISSN: 2663-628X; 2663-6298

Kinetic and thermodynamic parameters associated with the binding of 125I- anti AFP Antibody to AFP in both crude colorectal homogenate and partially- purified fractions were investigated. It was shown that the reaction in all studied groups follow pseudo- first order reaction kinetics.The value of kinetic parameters Ka, Kd, Kobs, K+1, K-1, (t1/2) ass., (t1/2)diss. and maximal binding capacity (Bmax) at 25oC for the binding of anti 125I-AFP antibody with its cytosolic antigen in benign colorectal tumor were found to be : 0.0543 x 1010 M-1, 15.064 x 10-10M, 0.0158 min-1, 4.086 x 106 M-1.min-1, 64.76x10-4 min-1, 43 min, 104.28 min and 29.14 Pmol/mg protein respectively, while 0.0538 x 1010 M-1, 15.142 x 10-10 M, 0.0163 min-1, 4.301 x 106 M-1.min-1, 67.63 x 10-4 min-1, 40 min, 79.66 min and 46.25 Pmol/mg respectively for the binding of anti 125I-AFP antibody with its cytosolic antigen in tissues of malignant colorectal tumor and at 4oC.  The maximum binding of partially purified AFP occurred at 25oC. The values ofKa and K+1 increased with increasing temperature. The Van’t Hoff plot demonstrated linear relationship between lnKa and 1/T, using crude colorectal homogenate partially purified AFP as AFP source. Plotting between ln K+1 and 1/T gave linear relationship called Arrheniuns relationship. The thermodynamic parameters ΔΗ˚, ΔG˚ and ΔЅ˚ for the formation of (125I- anti AFP Antibody / AFP) complex at the standard state had been determinedas well asEa, ΔΗ*, ΔG* and ΔЅ* which representing the transition state.