InterPro domain: IPR007466

Peptidyl-arginine deiminase (PAD) enzymes catalyse the deimination of the guanidino group from carboxy-terminal arginine residues of various peptides to produce ammonia. PAD from Porphyromonas gingivalis (Bacteroides gingivalis) (PPAD) appears to be evolutionarily unrelated to mammalian PAD ( IPR004303 ), which is a metalloenzyme. PPAD is thought to belong to the same superfamily as aminotransferase and arginine deiminase, and to form an alpha/beta propeller structure. This family has previously been named PPADH (Porphyromonas peptidyl-arginine deiminase homologues) [ 1 ]. The predicted catalytic residues in PPAD ( Q9RQJ2 ) are Asp130, Asp187, His236, Asp238 and Cys351 [ 2 ]. These are absolutely conserved with the exception of Asp187 which is absent in two family members. PPAD is also able to catalyse the deimination of free L-arginine, but has primarily peptidyl-arginine specificity. It may have a FMN cofactor [ 2 ].

1. A novel superfamily of enzymes that catalyze the modification of guanidino groups. Trends Biochem. Sci. 26, 465-8
2. Purification, characterization, and sequence analysis of a potential virulence factor from Porphyromonas gingivalis, peptidylarginine deiminase. Infect. Immun. 67, 3248-56