Thiol protease

Thiol proteases are a group of protease enzymes that utilize a cysteine residue in their active site to hydrolyze peptide bonds in proteins. They are also known as cysteine proteases and are one of the four main classes of proteases, along with serine proteases, aspartic proteases, and metalloproteases.

Structure and Mechanism

Thiol proteases have a common structure, which includes a catalytic dyad or triad that is essential for their enzymatic activity. The catalytic dyad typically consists of a cysteine and a histidine residue, while the triad also includes an asparagine residue. The cysteine residue acts as a nucleophile, attacking the peptide bond and leading to its cleavage.

Classification

Thiol proteases are classified into clans and families based on their structural similarities. The two main clans of thiol proteases are the papain-like (C1) and the caspase-like (C14). Each clan contains multiple families, which are further divided into subfamilies.

Biological Roles

Thiol proteases play crucial roles in a variety of biological processes, including protein degradation, apoptosis, and immune response. They are also involved in the pathogenesis of several diseases, such as cancer, inflammation, and parasitic infections.

Inhibition and Regulation

The activity of thiol proteases can be regulated by protease inhibitors, which bind to the active site and prevent the enzyme from cleaving its substrate. Several types of inhibitors exist, including small molecule inhibitors, protein inhibitors, and antibodies.

Clinical Significance

Due to their involvement in disease processes, thiol proteases are potential targets for therapeutic intervention. Several drugs that inhibit thiol proteases have been developed and are used in the treatment of diseases such as cancer and rheumatoid arthritis.

See Also

• Protease
• Cysteine
• Papain
• Caspase
• Protease inhibitors