Para-aminobenzoate synthase component I (pabB) is closely related to anthranilate synthase component I (trpE). The apparent orthologs of pabB in Aquifex aeolicus and Helicobacter pylori 26695 score well below most TrpE proteins because of a different architecture, in which the less strongly conserved N-terminal domain is absent. The noise cut off is set to exclude most examples of TrpE.