Catalytic properties of cathepsin B from human kidneys

: Two forms of cathepsin B isolated from human kidneys possess similar properties with hydrolysis of synthetic substrates. One of the forms is characterized by the higher specific activity with hydrolysis of synthetic substrates and proteins. Low-molecular peptides with nonpolar aminoacid residue in a site and hydrophilic C-end part inhibit reactions catalyzed by the both forms of cathepsin B. Such properties are not inherent in the apoenzymes of dehydrogenases and in albumin tested as inhibitors. It is found out that a thiol group of the active site does not interact with immobilized dithionitrobenzoic acid (DTNB) in contrast to the soluble one. A limited ability of cathepsin B to interact with native proteins is apparently, due to steric inhibitors which decreases accessibility of functional groupings of the active site.