Updated project metadata. The client-specificity of TMX3, TMX4 and TMX5 in cellula, was assessed by expressing mutant forms of the enzymes, where the last cysteine residue of the TMX’s CXXC catalytic sites has been mutated to alanine, which stabilizes the mixed disulfide that oxidoreductases establish with clients. Clients remain disulfide-bonded to the oxidoreductase and are identified upon co-immunoprecipitation and mass spectrometry analyses.