Comparison of host tissue and bacterial dipeptidyl peptidases in human gingival crevicular fluid by analytical isoelectric focusing

Earlier work has shown that gingival crevicular fluid (GCF) contains dipeptidyl peptidase (DPP) activities that resemble those in host tissue. Here, further comparisons were made with enzymes from suspected periodontal pathogens. Gingival tissue and GCF were collected from patients with chronic periodontitis. DPP II and DPP IV fractions with acid and alkaline pH optima, respectively, were separated from crude tissue extracts by gel-filtration chromatography. Bacterial cell sonicates were prepared from broth cultures of reference strains. There was moderate to strong DPP activity with Capnocytophaga spp., Porphyromonas gingivalis and Prevotella spp., very weak activity with Treponema denticola and no detectable activity with Actinobacillus actinomycetemcomitans or Fusobacterium nucleatum. Banding patterns in GCF, tissue and bacterial samples were compared on substrate-impregnated overlay membranes applied to isoelectric focusing gels. In gels washed with acid buffer, GCF had bands corresponding to tissue DPP II. Use of an alkaline washing buffer showed GCF activity which closely matched tissue DPP IV that had been pretreated with neuraminidase, an enzyme found by others in the gingival crevice. P. gingivalis gave multiple bands and several of these had counterparts in GCF. The apparent presence in GCF of the DPP from P. gingivalis is consistent with the association of this organism with destructive periodontitis.