Serine protease that cleaves preferentially after Arg residues (PubMed:22474388, PubMed:23904161, PubMed:25156428). Can also cleave after citrulline (deimidated arginine) and methylarginine residues (PubMed:25156428). Inhibited by SERPINA1, SERPINC1 and SERPING1. Stored in cytoplasmic granules and secreted as active enzyme in response to stimulation of neutrophils. Detected in peripheral blood neutrophil granulocytes, but not in other types of leukocytes. Detected in neutrophils and neutrophil precursors in bone marrow (at protein level) (PubMed:22474388, PubMed:23904161). Detected in myeloblasts and promyelocytes in bone marrow (PubMed:23904161). After cleavage of the signal peptide, the N-terminus is probably further processed by CTSC (PubMed:22474388, PubMed:23904161). Processing by CTSC is probably required for accumulation in cytoplasmic granules; in the absence of CTSC the protein does not accumulate (PubMed:23904161). N-glycosylated. Belongs to the peptidase S1 family.