Abstract
Historically, target enzymes of thioredoxin (Trx) were identified by biochemical studies of the enzymes. However, recent progress of the genome sequencing projects for various organisms made it possible to survey the candidates, by comprehensive and systematic efforts. In 2001, we reported a new method to capture the target candidates of Trx comprehensively using immobilized Trx mutant, which is able to form stable mixed-disulfide intermediate with target protein but not to facilitate the reduction of the disulfide bond of the target (Motohashi et al. PNAS, 98, 11224). This way we identified three potential target proteins (Prx-Q, cyclophilin, and rubisco small subunit) together with five known proteins for chloroplast Trx-m. Balmer et al. recently analyzed target proteins in spinach chloroplasts using the immobilized Trx-f and Trx-m mutants and suggested 26 proteins as potential targets for chloroplast Trx. Thus the redox cascade in the plant cell and the physiological significance are now revealed.
