Proteases are classified on the basis of catalytic mechanism, and seven known distinct classes are described: metallo, aspartic, cysteine, serine, glutamic, asparagine, and threonine.
Using a serine alcohol, display a wide range of functions.
Using a cysteine thiol, that include caspases which are involved in apoptosis and inflammation, and cathepsins which promote protein degradation.
Using a threonine secondary alcohol
Using an aspartate carboxylic acid, that include beta and gamma secretases, the two enzymes necessary to release amyloid beta peptides from the Alzheimer's disease associated amyloid precursor protein (APP).
Using a glutamate carboxylic acid
Using a metal, usually zinc. The Metalloprotease family includes aminopeptidases and endopeptidases, which are secreted, membrane-bound, or cytosolic.
Using an asparagine to perform an elimination reaction (not requiring water)