Two main nomenclatures for the primary structure are currently in use, the original one from which the first amino-acid starts with the signalling peptide and a second one where the first amino-acid starts counting from the prodomain ( proenzyme nomenclature ).
22.
Caspases exist as inactive proenzymes that undergo proteolytic processing by upstream caspases ( caspase-8,-9 ) at conserved aspartic residues to produce two subunits, large and small, that dimerize to form the active enzyme in the form of a heterotetramer.
