Phylogenetics and enzymology of plant quiescin sulfhydryl oxidase

► We demonstrate the expression of A. thaliana QSOX in a recombinant bacterial system. ► Recombinant A. thaliana QSOX shows robust sulfhydryl oxidase activity. ► Recombinant A. thaliana QSOX does not exhibit interdomain electron transfer. ► A thorough comparison of plant and metazoan QSOXs is presented. ► An analysis of QSOX cysteines throughout plant evolution is presented.