1G8F

ATP sulphurylase from Saccharomyces cerevisiae is able to catalyse the formation of adenosine-5-phosphosulphate. This functions as the first step in the incorporation of sulphate into biological molecules because it activates the sulphate towards nucleophilic attack by adding a good leaving group. The enzyme is part of a family of ATP sulphurylases (alpha/beta phosphodiesterase superfamily) which include those from the sulphur reducing bacteria, and proteins with dual kinase and sulphurylase activity found in mammals. The enzyme thus plays a vital role for cysteine and methionine biosynthetic pathways. While bacterial forms of ATPS form tetrameric hetero-dimer complexes which contain a GTPase subunit responsible for GTP hydrolysis and resulting activation of the catalytic reaction, homologues of ATPS from organisms such as yeast and plants exist as monomers or homo-oligomeric complexes and do not require GTP for activation.