Identification of a novel subtilisin-derived peptide, SC-(1–31), with cytotoxic activity

Subtilisins are alkaline serine proteases secreted by various species of Bacillus and can produce peptides by autolysis. A peptide from subtilisin NAT was found to disrupt the membrane of Streptococcus pneumoniae and to be cytotoxic only against tumor cell lines was found from subtilisin NAT. However, there has been little research on peptides derived from subtilisin Carlsberg, another famous subtilisin variant. In this research, we found another unique short peptide from subtilisin Carlsberg, which is produced by the fermentation of Bacillus licheniformis. This peptide had a molecular mass of 3225 Da and was identified as the N-terminal 31-amino acid residues of subtilisin Carlsberg, which has not been reported before. The peptide, named SC-(1-31), contains several cationic (pI = 9.83) and hydrophobic amino acid residues. It killed both cancer (Caco-2 and HeLa) and normal cell lines (WI-38) in concentration-dependent manners. The peptide was identified as a cytotoxic peptide based on its comparable toxicity towards cancer and normal cell lines. Liposome disruption assay suggested that this peptide may kill cells by disrupting the cell membrane.