Discrimination based on Gly and Arg/Ser at position 673 between dipeptidyl-peptidase (DPP) 7 and DPP11, widely distributed DPPs in pathogenic and environmental gram-negative bacteria

► Expression and site-directed mutagenesis were employed to define S46 members' substrate specificity. ► Gly673 in DPP7 and Arg/Ser673 in DPP11 were critical for the substrate specificity. ► All S46 members were assigned based on the single residue at position 673. ► A new phylogenic tree suggested two gene duplication events in the phylum Bacteroidetes.