[Characterization of Supersulfide in Serum Albumin and Its Therapeutic Application]

Recent studies have shown that proteins already possess supersulfides during the translation. However, the distribution and the role of supersulfides are not fully understood. In this review, we focus on supersulfides in biological fluids, especially in serum. Various methods for measuring supersulfides have been developed, and these methods have elucidated the presence of supersulfides in serum proteins including serum albumin. Since the levels of supersulfides in serum and serum albumin of patients with chronic kidney disease were lower than those in healthy subjects and recovered by hemodialysis, the levels of supersulfides in serum would be an indicator reflecting oxidative stress. In addition, it has long been known that serum albumin is responsible for sulfur transference. We have applied this phenomenon to the synthesis of sulfur-added albumin (S_n-HSA) by the reaction of serum albumin with sodium polysulfide (Na₂S_n). S_n-HSA suppressed the melanin production via scavenging oxidative stress. As described above, studies on the characterization of supersulfides in serum albumin may contribute to the monitoring of redox balance and prevention of oxidative stress-related diseases.