This family shows similarity to other isomerases. Putative identification ashexulose-6-phosphate isomerase has been reported. This family is conserved at better than 40% identity among the four known examples from three species: <taxon tax_id="562">Escherichia coli</taxon> (SgbU and SgaU), <taxon tax_id="727">Haemophilus influenzae</taxon>, and <taxon tax_id="2104">Mycoplasma pneumoniae</taxon>. The rarity of the family, high level of conservation, and proposed catabolic role suggests lateral transfer may be a part of the evolutionary history of this protein. Putative hexulose-6-phosphate isomerase