FIGURE 7.

Proposed catalytic mechanism of Srx from S. cerevisiae. The recycling mechanism involves the attack of the Cys⁴⁸ of Srx on the sulfur atom of Cys⁸⁴ of the thiosulfinate intermediate, leading to the release of the oxidized Cys⁴⁸/Cys⁸⁴ Srx with intramolecular disulfide bond and of the sulfenic acid PrxSOH product. The Cys⁴⁸/Cys⁸⁴ Srx is then reduced by attack of the Trx catalytic Cys on Cys⁴⁸ to form a Trx-Srx mixed disulfide, followed by regeneration of reduced Srx by attack of the recycling Cys of Trx. P, Prx; S, Srx; C_P, peroxidatic Cys; C₈₄, Srx catalytic Cys; C₄₈, Srx regeneration Cys; T, thioredoxin.