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). {ECO:0000269|PubMed:22474388, ECO:0000269|PubMed:23904161, ECO:0000269|PubMed:25156428}. This is the function of Ensembl gene identifier ENSG00000185198 (PRSS57, serine protease 57).