proteinaasi

Proteinaasi, or proteases, are enzymes that catalyze the hydrolysis of peptide bonds in proteins, using water to release shorter fragments. They are a diverse group of hydrolases found in all living organisms and are essential for digestion, protein turnover, and regulation of cellular processes.

They are classified by catalytic mechanism. Serine proteases use a Ser-His-Asp triad (for example trypsin and chymotrypsin). Cysteine proteases use a cysteine residue (for example papain). Metalloproteases require a metal ion such as zinc (for example matrix metalloproteases). Aspartic proteases rely on two aspartates (for example pepsin). Threonine proteases (for example the proteasome) form another group. Substrate specificities and inhibitors vary by class.

Many proteases are produced as inactive zymogens and activated proteolytically. Activity is regulated by inhibitors, pH, cofactors, and subcellular localization. Common inhibitors include serine protease inhibitors, cystatins for cysteine proteases, TIMPs for metalloproteases, and lysosomal inhibitors.

In biology, proteases function in digestion (stomach and pancreas), intracellular proteolysis (proteasome), antigen processing, inflammation, and tissue remodeling. They also participate in signaling by processing receptors and ligands.

Clinically and industrially, proteases are major tools and targets. In medicine, protease inhibitors are used against viruses and cancer; proteasome inhibitors are anticancer agents. Industrial uses include detergents, food processing, and leather, while enzymes serve as research tools and in assays.