ABSTRACT
The thioredoxin (TRX) system, which is composed of NADPH, TRX, and TRX reductase, has been characterized from a wide variety of prokaryotic and eukaryotic species (1,2). TRX is a small multifunctional and ubiquitous protein having a redox-active disulfide/dithiol within the conserved active site sequence -Cys-Gly-Pro-Cys-located on a protru sion in its three-dimensional structure (1,2). Oxidized TRX with a dis ulfide on its active site is reduced by NADPH and TRX reductase, and reduced TRX can function as a general protein disulfide reductase (1,2). Adult T-cell leukemia-derived factor (ADF) was first defined as an IL2Ra chain inducing factor produced by human T-cell lymphotropic virus type 1 (HTLV-l)-transformed T cells (3). Subsequent purifica tion and gene cloning have revealed that ADF is human TRX (4). TRX/ ADF has been reported to possess multiple biological functions and to regulate different systems via thiol redox control, including the activa tion of several essential enzymes, the reduction of oxygen radicals, and the redox regulation of certain receptors and transcription factors (1,2,5).
