CysH（Phosphoadenosine phosphosulfate reductase) is a member of the PAPS reductase family， specifically those acting on a sulfur group of donors with a disulfide as acceptor. The 3 substrates of the CysH enzyme are adenosine 3’，5’-bisphosphate， sulfite， and thioredoxin disulfide， whereas its two products are 3’-phosphoadenylyl sulfate and thioredoxin.
