Salivary histatin 5 is an inhibitor of both host and bacterial enzymes implicated in periodontal disease.
One of the salient features of periodontitis and gingivitis is the increase in the levels of bacterial and host-derived proteolytic enzymes in oral inflammatory exudates. This study evaluated the potential of histatin 5, a 24-residue histidine-rich salivary antimicrobial protein, to inhibit these enzymes. Using biotinylated gelatin as a substrate, histatin 5 was found to inhibit the activity of the host matrix metalloproteinases MMP-2 and MMP-9 with 50% inhibitory concentrations (IC50s) of 0.57 and 0.25 microM, respectively. To localize the domain responsible for this inhibition, three peptides containing different regions of histatin 5 were synthesized and tested as inhibitors of MMP-9. Peptides comprising residues 1 to 14 and residues 4 to 15 of histatin 5 showed much lower inhibitory activities (IC50, 21.4 and 20.5 microM, respectively), while a peptide comprising residues 9 to 22 showed identical activity to histatin 5 against MMP-9. These results point to a functional domain localized in the C-terminal part of histatin 5. To evaluate the effect of histatin 5 on bacterial proteases, a detailed characterization of histatin 5 inhibition of gingipains from Porphyromonas gingivalis was carried out using purified Arg- and Lys-specific enzymes. Kinetic analysis of the inhibition of the Arg-gingipain revealed that histatin 5 is a competitive inhibitor, affecting only the Km with a K(i) of 15 microM. In contrast, inhibition of Lys-gingipain affected both the Km and Vmax, suggesting that both competitive and noncompetitive competitive processes underlie this inhibition. The inhibitory activity of histatin 5 against host and bacterial proteases at physiological concentrations points to a new potential biological function of histatin in the oral cavity.
Gusman
H
H
Department of Periodontology and Oral Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts 02118-2392, USA.
Travis
J
J
Helmerhorst
E J
EJ
Potempa
J
J
Troxler
R F
RF
Oppenheim
F G
FG
D018829:Adhesins, Bacterial; D003546:Cysteine Endopeptidases / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D000080867:Gingipain Cysteine Endopeptidases; D006388:Hemagglutinins / Q000187:drug effects; D054808:Histatins; D007976:Leupeptins / Q000494:pharmacology; D061965:Matrix Metalloproteinase Inhibitors; D010510:Periodontal Diseases / Q000209:etiology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D012471:Salivary Proteins and Peptides / Q000494:pharmacology*
D018829:Adhesins, Bacterial; D000080867:Gingipain Cysteine Endopeptidases; C068075:HTN3 protein, human; D006388:Hemagglutinins; D054808:Histatins; D007976:Leupeptins; D061965:Matrix Metalloproteinase Inhibitors; D011480:Protease Inhibitors; D012471:Salivary Proteins and Peptides; D003546:Cysteine Endopeptidases; C032854:leupeptin