This is a family of 3-deoxy-D-manno-oct-2-ulosonic acid 3-hydroxylases, which catalyze the conversion of 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) to D-glycero-D-talo-oct-2-ulosonic acid (Ko). It contains a potential iron-binding motif, HXDX(n)H (n>40). Hydroxylation activity is iron-dependent.