Cystatins in Body Fluids

The distribution in body fluids of the different cystatins is remarkably different (Fig. 3). For example, while cystatin C is present in appreciable amounts in all investigated body fluids, cystatins S, SN, and SA are virtually confined to saliva, tears, and seminal plasma (Al). Cystatin D is present only in saliva and tear fluid (Al, F3). In some body compartments, e.g., spinal fluid, cystatin C represents more than 90% of the total molar concentration of cysteine protease 

Equilibrium Constants for Dissociation of Complexes between Human Cystatins and Cysteine Proteases Ki (nM) 

Cystatin Cathepsin B Cathepsin L Cathepsin S Cathepsin H Papain 

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