A proposed reaction mechanism for rice NADPH thioredoxin reductase C, an enzyme with protein disulfide reductase activity

NADPH thioredoxin reductase C ( NTRC) is an interesting NTR with a thioredoxin (Trx) domain at the C-terminus, able to conjugate both activities for 2-Cys peroxiredoxin (Prx) reduction. NTRC is dimeric in the presence of NADPH and interacted with dimeric 2-Cys Prx through the Trx module by a mixed disulfide between Cys377 of NTRC and Cys61 of the 2-Cys Prx. NTRC variants of both NTR and Trx active sites were inactive, but 1: 1 mixtures of both variants allowed partial recovery of activity suggesting inter-subunit transfer of electrons during catalysis. Based on these results we propose a model for the reaction mechanism of NTRC.