Superoxide Dismutase Activity of the Naturally Occurring Human Serum Albumin–Copper Complex without Hydroxyl Radical Formation

The superoxide radical anion (O 2 .− ) is biologically toxic and contributes to the pathogenesis of various diseases. Here we describe the superoxide dismutase (SOD) activity of human serum albumin (HSA) complexed with a single Cu II ion at the N‐terminal end (HSA–Cu complex). The structure of this naturally occurring copper‐coordinated blood serum protein has been characterized by several physicochemical measurements. The O 2 .− dismutation ability of the HSA–Cu (1:1) complex is almost the same as that of the well‐known SOD mimics, such as Mn III ‐tetrakis( N ‐methylpyridinium)porphyrin. Interestingly, the HSA–Cu complex does not induce a subsequent Fenton reaction to produce the hydroxyl radical (OH . ), which is one of the most harmful reactive oxygen species .