väike 12kDa valk, mille aktiivtsentri tsüsteiinijäägid osalevad tiool-disulfiid vahetusreaktsioonides, Thioredoxin is a class of small redox proteins known to be present in all organisms. It plays a role in many important biological processes, including redox signaling. In humans, thioredoxins are encoded by TXN and TXN2 genes. Thioredoxin is a 12 kDa protein having cysteine residues in the active centre which thiol-disulphate exchange reaction. Activates Calvin-Benson cycle enzymes by reducing their disulfide bonds at the expense of electrons from ferredoxin.