PAPSS2 (3'-Phosphoadenosine 5'-Phosphosulfate Synthase 2): PAPSS2 is a gene that encodes an enzyme essential for the production of PAPS (3'-phosphoadenosine 5'-phosphosulfate), a key sulphate donor in various sulphation reactions. It plays an important role in the metabolism of hormones, drugs, and other molecules. Mutations in PAPSS2 can affect skeletal development and lead to disorders such as spondyloepimetaphyseal dysplasia.