Uncharacterized subgroup of the CYTH-like superfamily having an associated CHAD domain
This subgroup belongs to the CYTH-like (also known as triphosphate tunnel metalloenzyme (TTM)-like) superfamily. Members of this superfamily hydrolyze triphosphate-containing substrates, require metal cations as cofactors, and have a unique active site located at the center of an eight-stranded antiparallel beta barrel tunnel (the triphosphate tunnel). A number of proteins in this subgroup also contain a C-terminal CHAD (Conserved Histidine Alpha-helical Domain) domain which may participate in metal chelation or act as a phosphor-acceptor. The name CYTH originated from the gene designation for bacterial class IV adenylyl cyclases (CyaB) and from thiamine triphosphatase. Class IV adenylate cyclases catalyze the conversion of ATP to 3',5'-cyclic AMP (cAMP) and PPi. Thiamine triphosphatase is a soluble cytosolic enzyme which converts thiamine triphosphate to thiamine diphosphate. This domain superfamily also contains RNA triphosphatases, membrane-associated polyphosphate polymerases, tripolyphosphatases, nucleoside triphosphatases, nucleoside tetraphosphatases and other proteins with unknown functions. Proteins of this subgroup have not been characterized.