Serine protease that cleaves preferentially after Arg residues. Can also cleave after citrulline (deimidated arginine) and methylarginine residues. Stored in cytoplasmic granules and secreted as active enzyme in response to stimulation of neutrophils. After cleavage of the signal peptide, the N-terminus is probably further processed by CTSC. Processing by CTSC is probably required for accumulation in cytoplasmic granules; in the absence of CTSC the protein does not accumulate. N-glycosylated. Belongs to the peptidase S1 family.