KNG1 and infection: In the context of infections, kinins can be directly liberated from the kininogens by the action of microbial cysteine proteases, such as gingipain from Porphyromonas gingivalis (Imamura et al., 1994), staphopain A from Staphylococcus aureus (Imamura et al., 2005), streptopain from Streptococcus pyogenes (Herwald et al., 1996), and cruzipain (Del Nery et al., 1997; Scharfstein et al., 2000; Monteiro et al., 2006).