Uric acid. Characterization of its interaction with human serum albumin.

Binding of sodium urate to human serum albumin (HSA) was measured by continuous ultrafiltration at pH 7.4 and ionic strength 0.16 over the concentration range 1-13 mg/100 ml. The percent sodium urate bound to 5 g/100 ml HSA was constant over this concentration range: 30.3 (SE+/-0.6)% being bound at 4 degrees C, 22.6+/-0.3% at 22.5 degrees C, and 19.6+/-0.3% at 37 degrees C. Derived association constants, assuming one binding site were 6.0 x 10(2) M(-1) (4 degrees C), 4.47 x 10(2) M(-1) (22.5 degrees C), and 3.88 x 10(2) M(-1) (37 degrees C).