Catalyzes the removal of dipeptides from the N-terminus of oligopeptides. Prefers Ala and hydrophobic residues except Pro at the P1 position, and has no preference for P2 residues. Shows high dipeptidyl peptidase activity toward the synthetic substrates Lys-Ala-, Gly-Phe-, Met-Leu-, and Ser-Tyr-methylcoumaryl-7-amide (MCA), and slowly hydrolyzes Val-Tyr-MCA. Is likely involved in amino acid metabolism and bacterial growth of asaccharolytic P.gingivalis, that utilizes amino acids from extracellular proteinaceous nutrients as energy and carbon sources. kcat is 5638 sec(-1) with Gly-Phe-MCA as substrate. kcat is 7577 sec(-1) with Lys-Ala-MCA as substrate. kcat is 5562 sec(-1) with Met-Leu-MCA as substrate. kcat is 744 sec(-1) with Lys-Phe-MCA as substrate. kcat is 1329 sec(-1) with Ser-Tyr-MCA as substrate. kcat is 490 sec(-1) with Lys-Leu-MCA as substrate. kcat is 299 sec(-1) with Lys-Val-MCA as substrate (at 37 degrees Celsius and pH 6.0). Optimum pH is 6.7, using Lys-Ala-MCA as substrate. Homodimer. Belongs to the peptidase S9C family.