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cystatin 4 (cystatin-S, cystatin-SA3, salivary acidic protein-1, CST4)
Function:
- strongly inhibits papain & ficin,
- partially inhibits stem bromelain & bovine cathepsin C
- but does not inhibit porcine cathepsin B or clostripain
- papain is inhibited non-competitively
- phosphorylated at both its N- & C-terminal regions
Structure: belongs to the cystatin family
Compartment: secreted
Expression: found in saliva, tears, urine & seminal fluid
Note:
- human saliva appears to contain several cysteine proteinase inhibitors immunologically related to cystatin S but that differ in their specificity due to amino acid sequence differences
General
cystatin
Properties
SIZE: entity length = 141 aa
MW = 16 kD
COMPARTMENT: extracellular compartment
MOTIF: signal sequence {1-20}
Ser phosphorylation site {S21}
Ser phosphorylation site {S23}
glycine residue {32}
Secondary area of contact {76-80}
cysteine residue {C94}
MODIFICATION: cysteine residue {C104}
cysteine residue {C104}
MODIFICATION: cysteine residue {C94}
cysteine residue {C118}
MODIFICATION: cysteine residue {C138}
cysteine residue {C138}
MODIFICATION: cysteine residue {C118}
INHIBITS: cysteine proteinase
Database Correlations
OMIM 123857
UniProt P01036
Entrez Gene 1472
References
UniProt :accession P01036