Interaction of myo-inositol hexaphosphate (MIHP) with beta-globulin from Sesamum indicum L. Kinetics and thermodynamics.
beta-Globulin, the low molecular weight protein fraction from Sesamum indicum L., interacts with myo-inositol hexaphosphate (MIHP) maximally at pH 3.0, with concomitant precipitation up to 85 +/- 2% at an MIHP concentration of 8 x 10(-4) M. The kinetics of interaction as followed by stopped-flow spectrophotometry suggested the reaction to be of pseudo first-order, having an initial fast step followed by a relatively slow step of rate constants 1.9 x 10(-2) s-1 and 1.2 x 10(-3) s-1, respectively at 1 x 10(-4) M MIHP concentration. The analysis of the complex indicated the presence of polymer as seen in sedimentation velocity experiment. This was accompanied by conformational change of a three-fold decrease in beta-structure and also an increase in fluorescence emission intensity accompanied with a red shift from 330 to 334 nm. Stoichiometric analysis of MIHP binding suggested four independent binding sites for MIHP, with a free energy change, delta G zero = 5.1 kcal mol-1 resulting from a binding constant of 3.6 x 10(3) M-1.
Rajendran
S
S
Food Chemistry Department, Central Food Technological Research Institute, Mysore, India.
Prakash
V
V
D001609:Beta-Globulins / Q000378:metabolism*; D001665:Binding Sites; D011232:Chemical Precipitation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010833:Phytic Acid / Q000378:metabolism*; D010944:Plants / Q000378:metabolism; D011487:Protein Conformation; D013816:Thermodynamics
D001609:Beta-Globulins; D010833:Phytic Acid