title: Characterization of a new cysteine proteinase inhibitor of human saliva, cystatin SN, which is immunologically related to cystatin S.
abstract: A new cysteine proteinase inhibitor, cystatin SN, was purified from human whole saliva by chromatography with DE32, Sephacryl S200, and CM-Sepharose CL6B. Cystatin SN is immunologically related to cystatin S and both inhibitors have a similar molecular mass of about 13 kDa. The new inhibitor, however, was clearly distinguished from cystatin S by its much higher pI value. These inhibitors showed similar inhibitory activity for ficin, but cystatin SN was a much better inhibitor for papain and dipeptidyl peptidase I. The amino acid sequence of cystatin SN deduced in the light of the known structure of cystatin S indicates that they have 10 different amino acid residues in the sequence comprising in total 113 residues.
mesh_terms: D000595:Amino Acid Sequence; D003429:Cross Reactions; D015891:Cystatins; D003546:Cysteine Endopeptidases; D006801:Humans; D011480:Protease Inhibitors; D012463:Saliva / Q000032:analysis*; D055333:Salivary Cystatins; D012471:Salivary Proteins and Peptides / Q000032:analysis / Q000276:immunology* / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: C525171:CST1 protein, human; C525173:CST4 protein, human; D015891:Cystatins; D011480:Protease Inhibitors; D055333:Salivary Cystatins; D012471:Salivary Proteins and Peptides; D003546:Cysteine Endopeptidases