Proteases from Entamoeba spp. and Pathogenic Free-Living Amoebae as Virulence Factors

Table 1

Cysteine proteases of Entamoeba histolytica that degrade host proteins and their implication in virulence.

Tissue or protein	Purified	Name	Mr (kDa)	Comment, localization	Reference
ECM components
Collagen	Yes	EhCP1	27	In vitro, surface	[6]
	Yes	EhCP2	26	In vitro, membrane-associated	[7]
	Yes	EhCP112	35.5	In vitro (zymogram), surface	[8]
	Yes	EhCP5	30	In vitro (zymogram), and it is essential ex vivo for the cleavage of the collagen network, surface	[9, 10]
	Yes	—	56	In vitro, secreted	[11]
	No	—	72	In vitro (zymogram), crude extracts and EDG	[12]
	Yes	—	27–29	In vitro	[13]
Laminin	Yes	EhCP4	26	In vitro, secreted and nuclear	[14]
	Yes	—	56	In vitro, secreted	[11]
	Yes	—	27–29	In vitro	[13]
Fibronectin	Yes	EhCP112	35.5	In vitro (zymogram), surface	[8]
	Yes	—	56	In vitro, secreted	[11]
	Yes	—	27–29	In vitro	[13]
Gelatin	No	—	110, 68, 56, and 22	Induced by collagen, conditioned medium	[15]
Immunoglobulins
IgA	Yes	EhCP4	26	In vitro, secreted and nuclear	[14]
	Yes	—	70	In vitro	[16]
IgG	Yes	EhCP5	30	In vitro, surface	[9]
	Yes	EhCP4	26	In vitro, secreted and nuclear	[14]
	Yes	EhCP1	27	In vitro, surface	[17]
	Yes	—	56	In vitro, secreted	[11]
Complement
C3	Yes	EhCP4	26	In vitro, secreted and nuclear	[14]
	Yes	EhCP1	27	In vitro, surface	[17]
	Yes	—	56	In vitro	[18]
C3a and C5a	Yes	—	56	In vitro	[19]
Cytokines
proIL-18	Yes	EhCP4	26	In vitro, secreted and nuclear	[14]
	Yes	EhCP5	30	In vitro, surface	[20]
	Yes	EhCP1	27	In vitro, surface	[17]
proIL-1β	Yes	EhCP1	27	In vitro, surface	[21, 22]
		EhCP2	26	In vitro, membrane-associated	[21, 22]
Iron-containing proteins
Hemoglobin	Yes	EhCP112	35.5	In vitro (zymogram), surface	[8]
	Yes	EhCP5	30	In vitro (zymogram), surface	[9]
	Yes	—	41, 27	In vitro, intracellular	[23]
	No	—	32, 40	In vitro, total extract	[24]
	Yes	—	22	In vitro	[25]
	Yes	—	16	In vitro	[26]
	No	—	116, 82, 28, and 21	Human, porcine, and bovine Hb in vitro (zymogram)	[27]
Transferrin	No	—	130, 43, 20, and 6	Total extract; in vitro (zymogram)	[28]
	No	—	130, 70, 50, 35, and 30	Conditioned medium; in vitro (zymogram)	[28]
Lactoferrin	No	—	250, 100, 40, and 22	Total extract; in vitro (zymogram)	[29]
Ferritin	No	—	100, 75, and 50	Total extract; in vitro (zymogram)	[30]
Other proteins or tissues
Mucin	Yes	EhCP5	30	In vitro (zymogram), although ex vivo is not needed to cross the mucus, surface	[9, 31]
Proteoglycan	Yes	EhCP2	26	In vitro, membrane-associated	[7]
Villin	Yes	EhCP1	27	In vitro, surface	[14]
	Yes	EhCP4	26	Iin vitro, secreted and nuclear	[14]
Fibrinogen	Yes	EhCP5	30	In vitro (zymogram), surface	[9]
BSA	Yes	EhCP5	30	In vitro (zymogram), surface	[9]

EDG: electron-dense granules.