Recombinant Human Cystatin-S (CST4)

Uniprot Id

P01036

Target Species

Human

Target Name

CST4

Target Full Name

Cystatin-S

Target Function

This protein strongly inhibits papain and ficin, partially inhibits stem bromelain and bovine cathepsin C, but does not inhibit porcine cathepsin B or clostripain. Papain is inhibited non-competitively.

Target Subcellular Location

Secreted.

Target Protein Families

Cystatin family

Target Tissue Specificity

Expressed in submandibular and sublingual saliva but not in parotid saliva (at protein level). Expressed in saliva, tears, urine and seminal fluid.

Target Synonyms

Cst4; Cystatin 4; Cystatin S precursor ; Cystatin SA III; Cystatin-4; Cystatin-S; Cystatin-SA-III; CYTS_HUMAN; MGC71923; Salivary acidic protein 1

Target Background

The cystatin superfamily encompasses proteins that contain multiple cystatin-like sequences. Some of the members are active cysteine protease inhibitors, while others have lost or perhaps never acquired this inhibitory activity. There are three inhibitory families in the superfamily, including the type 1 cystatins (stefins), type 2 cystatins and the kininogens. The type 2 cystatin proteins are a class of cysteine proteinase inhibitors found in a variety of human fluids and secretions. The cystatin locus on chromosome 20 contains the majority of the type 2 cystatin genes and pseudogenes. This gene is located in the cystatin locus and encodes a type 2 salivary cysteine peptidase inhibitor. The protein is an S-type cystatin, based on its high level of expression in saliva, tears and seminal plasma. The specific role in these fluids is unclear but antibacterial and antiviral activity is present, consistent with a protective function.