HINT (histidine triad nucleotide-binding protein) subgroup: Members of this CD belong to the superfamily of histidine triad hydrolases that act on alpha-phosphate of ribonucleotides. This subgroup includes members from all three forms of cellular life. Although the biochemical function has not been characterised for many of the members of this subgroup, the proteins from Yeast have been shown to be involved in secretion, peroxisome formation and gene expression.