Thyroxine binding properties of glycosylated human serum albumin as measured by fluorescence.
Thyroid hormone, thyroxine (T4) binding to glycosylated human serum albumin (G-HSA), and native human serum albumin (HSA) were studied as a function of pH using the fluorescence method. T4 binding affinity for G-HSA was remarkably reduced in an alkaline pH as compared with the native HSA. The thermodynamic parameters for binding are estimated at pH 7.5: (a) for G-HSA, delta G = -8.50 +/- 0.04 kcal mol-1 (30 degrees C), delta H = -5.2 kcal mol-1, delta S = +11 e.u.; (b) for HSA, delta G = -8.89 +/- 0.04 kcal mol-1 (30 degrees C), delta H = -3.5 kcal mol-1, delta S = +18 e.u. These results suggest that the glycosylation of HSA causes a variation in the electrostatic interaction between T4 and HSA.
Okabe
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N
Faculty of Pharmaceutical Sciences, Kinki University, Osaka, Japan.
Yoshida
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S
D006031:Glycosylation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D013974:Thyroxine / Q000378:metabolism*
D012709:Serum Albumin; D013974:Thyroxine