May play a dual role in regulation of ESX-1 secretion and virulence. Acts as a protease that cleaves EspB. Essential for ESX-1 function, required for early replication in macrophages and full virulence in mice. Cell wall-associated. Constitutively expressed during growth in culture (PubMed:10974545). Induced during growth in macrophages (PubMed:12366866). Deletion mutant fails to secrete EsxA and EspB and replicates poorly in mice. Belongs to the peptidase S8 family. Was originally thought to be proteolytically processed intracellularly.