ABSTRACT
Thioredoxin (TRX) is a ubiquitous protein with two redox-active cys tine residues in the active center, having the amino acid sequence (-CysGly-Pro-Cys-) (1). TRX was first isolated in 1964 as the hydrogen donor for the enzymatic synthesis of deoxyribonucleotides by ribonucleotide reductase in Escherichia co li (2). In addition, TRX is an essential sub unit of phage T7 DNA polymerase (3). The human TRX is known as the autocrine growth factor derived from the human Epstein-Barr vi rus (EBV)-containing B-lymphoblastoid cell lines 3B6, and was termed “3B6-interleukin-l(3B6-IL-l)” (4). Inducer of the interleukin-2 recep tor (IL-2R) on T-cell lines transformed by human T-cell lymphotrophic virus-I (HTLV-I) was named “adult T-cell leukemia (ATL) (5)-derived factor (ADF)” (6). It was found that 3B6-IL-1 and ADF were identical (7). Moreover, it has been reported that TRX is identical to the human eosinophil cytotoxicity-enhancing factor, which enhances human eosi-
nophil cytotoxic function in vitro (8), and the early pregnancy factor, which has a vital role in the development and immune protection of the embryo (9). TRX has various biological activities as a hydrogen donor, including reduction of insulin (10), activation of glucocorticoid recep tor (11), upregulation of nuclear factor к В binding (12), protein disul fide isomerase activity (13), activation of protein kinase C (14), an radi cal scavenging activity (15,16). In addition, TRX plays an important role in protection against various stresses including tumor necrosis factor a (17), lethal doses of irradiation (18), (19) and ultraviolet irradiation (20).
