Disulfide between Cys392 and Cys438 of human serum albumin is redox-active, which is responsible for the thioredoxin-supported lipid peroxidase activity.
Human serum albumin (HSA) is an abundant protein found in blood plasma and extracellular fluids. Previously, we found that HSA has a distinct thioredoxin (Trx)-dependent lipid peroxidase activity in the presence of palmitoyl-CoA. In this paper, we identified the redox-active disulfide, which can be specifically reduced by Trx, responsible for the Trx-dependent lipid peroxidase activity. The IIB-III fragment of HSA (Pro299-Leu585) sustained the Trx-dependent lipid peroxidase activity. Chemical modification of the Trx-reduced IIB-III with a thiol-specific modification agent resulted in a complete loss of the peroxidase activity. The analysis of tryptic-peptides derived from the inactivated HSA and IIB-III revealed that Cys392 and Cys438, which exist as an intramolecular disulfide bond in HSA, were preferentially modified in both HSA and IIB-III. Taken together, these results suggested that HSA has a capability to reduce lipid hydroperoxide with the use of Trx as an in vivo electron donor, and that the redox-active disulfide between Cys392 and Cys438 acts as a primary site of the catalysis for the Trx-linked lipid peroxidase activity.
Cha
Mee-Kyung
MK
Department of Biochemistry, Paichai University, Taejon 302-735, Republic of Korea.
Kim
Il-Han
IH
D001665:Binding Sites; D002384:Catalysis; D003545:Cysteine / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry*; D006801:Humans; D015227:Lipid Peroxidation; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry; D010544:Peroxidases / Q000737:chemistry*; D012709:Serum Albumin / Q000737:chemistry*; D013879:Thioredoxins / Q000737:chemistry*
D004220:Disulfides; D010446:Peptide Fragments; D012709:Serum Albumin; D013879:Thioredoxins; D010544:Peroxidases; D003545:Cysteine