Enzyme Inhibitors

Leupeptin hemisulfate (Ac-Leu-Leu-argininal) is a reversible inhibitor of serine and cysteine endopeptidases. Leupeptin hemisulfate is capable of inhibiting plasmin, trypsin, papain, kallikrein, calpain and cathepsin B. Leupeptin is usually used in a concentration range of 10 to 100μM. Leupeptin is widely used in many protease inhibitor cocktails due to its potency, low toxicity, and range of inhibition. Leupeptin is also used in a quantitative assay to measure macroautophagic flux in mammals and is being investigated for its use in treating malaria.

Pepstatin A is a competitive, reversible aspartic protease inhibitor and inhibits proteases such as pepsin, chyomsin, renin, HIV proteases, and cathepsins D and E. Peptstatin A is highly selective and is often used in a mixture with other enzyme inhibitors. In vitro studies have shown pepstatin A is the only aspartic acid inhibitor that exhibits inhibitory effects on HIV proteases.

Pepstatin A is effective at inhibiting most affected proteases at a concentration of 1μM, but can inhibit pepsin at the picomolar range of concentrations. It is believed to function by way of a collected-substrate inhibition mechanism. Pepstatin A may also suppress differentiation of osteoclasts by inhibiting phosphorylation of MAP kinase and inhibiting NFATc1 expression.

Sodium orthovanadate is a general competitive inhibitor of tyrosine specific phosphatases, acid and alkaline phosphatases and ATPases. Phosphatase inhibition from Vanadate may be completely reversed by dilution or by the addition of EDTA.

Trypsin inhibitor is a serine protease inhibitor from soybeans that is specific for trypsin and trypsin-like proteases. Trypsin inhibitor from soybeans is a monomeric protein containing 181 amino acid residues in a single polypeptide chain cross-linked by two disulfide bridges. Soybean trypsin inhibitor forms a 1:1 complex with the active protease site. Inhibition may be reversed and is pH dependent. The optimal pH for trypsin binding is 8.0.