ADP-riboxanase effector that inhibits host cell pyroptosis (PubMed:23684308, PubMed:34409271, PubMed:34671164). Acts by mediating arginine ADP-riboxanation of host CASP4/CASP11, blocking CASP4/CASP11 autoprocessing (PubMed:34671164). This prevents CASP4 activation and ability to recognize and cleave GSDMD, thereby inhibiting LPS-induced pyroptosis (PubMed:34671164). ADP-riboxanation takes place in two steps: OspC3 first catalyzes ADP-ribosylation of target Arg, and then initiates a deamination to remove one N-omega group (PubMed:34671164). L-arginyl-[protein] + NAD(+) = ADP-riboxanated L-argininyl-[protein] + H(+) + NH4(+) + nicotinamide Secreted via the type III secretion system (TTSS). Host cells display increased pyroptosis. Belongs to the OspC family.