Potential roles and mechanisms of bacterial peptidylarginine deiminase in dental biofilm mediated by Porphyromonas gingivalis.

Background: Porphyromonas gingivalis, a keystone oral pathogen, secretes the enzyme peptidylarginine deiminase (PPAD), which catalyzes protein citrullination and is implicated in both dental biofilm formation and the pathogenesis of systemic inflammatory diseases. Objective: This review aims to synthesize current knowledge on PPAD, with a specific focus on its mechanistic roles in oral biofilm dynamics and its potential contribution to the development of periodontitis and rheumatoid arthritis (RA). Design: A comprehensive literature search was conducted using the PubMed database up to August 2025, employing keywords including 'PPAD', 'Porphyromonas gingivalis', 'citrullination', 'dental biofilm', 'periodontitis', and 'rheumatoid arthritis'. Results: PPAD contributes critically to biofilm pathogenicity by modulating microbial pH, citrullinating virulence factors, and facilitating polymicrobial interactions. It promotes bacterial adhesion, disrupts host immunity, and sustains local inflammation. Systemically, PPAD-generated citrullinated antigens may trigger autoimmune responses, potentially linking periodontitis to RA. Conclusion: PPAD represents a promising biomarker and therapeutic target for mitigating oral-systemic disease progression. Future research should prioritize elucidating its spatiotemporal regulation within biofilms and its immune-dysregulating effects to guide precision interventions.