Impact of proteolytic enzymes in colorectal cancer development and progression

Table 1 Categories and main properties of proteolytic enzymes

Property	Cysteine proteases	Serine proteases	Aspartic proteases	Metallo proteases
Active site	Cysteine	Serine	Aspartic acid	Zinc
Optimum pH	7-9	3-7	2-4	5-9
Location	Lysosomes	Intra-extracellular	Lysosomes	Intra-extracellular
Examples	Cathepsins	Elastase	Pepsinogen I-II	Collagenase
	B, L, C, H	Trypsin	Cathepsins D, E	Stromelysin
		PA: uPA, tPA	Gelatinase	Matrilysin
Inhibitors	Cystatin	Antitrypsin	Unknown	TIMP
		Antithrombin III
		PAI

PA: Plasminogen activators; uPA: Uroinase-type plasminogen activator; tPA: Tissue-type plasminogen activator; PAI: Plasminogen activator inhibitor; TIMP: Tissue inhibitor of metalloproteinases.