Table 1.

Potential host proteases that inhibit SARS-CoV-2 virus.

Inhibitors	Location	Mechanism Involved	References
Neutrophil elastase	Bone marrow	Affects the levels of growth factor alpha and stimulates mucus secretion	Nakamura et al. (1992); Roghanian and Sallenave (2008)
TMPRSS2 HAT TTSPs TMPRSS11a Cathepsin B/L Factor Xa	Transmembrane Histone protein Transmembrane Transmembrane Endosome Liver	Spike protein priming leading to ACE2 receptor–dependent viral entry.	Bertram et al. (2011); Seth et al. (2020)
Chymase Tryptase	Lining of intestine Connective tissue	Due to absence of protease inhibitors in lungs, uncontrolled elevated expression of granzymes lead to degradation of extracellular matrix and induce the induction of pro-inflammatory cytokines	Pejler et al. (2007)
Kallikrein-related peptidase 13	Chromosome	Involved in assisting human coronavirus entry by specific cleaving at S1/S2 site	Milewska et al. (2020)
KLK1 KLK5	Kidney, pancreas Epidermis	Involved in cleavage of hemagglutinin, enhancing the viral production	Leu et al. (2015); Magnen et al. (2017)
Proteinase 3	Neutrophils	Overexpression leads to uncontrolled degradation of extracellular matrix and inflammatory responses	Van der Geld et al. (2001)
Cathepsin C	Lysosome	Activation of several pro-inflammatory serine proteases	Méthot et al. (2007)
Granzymes A, B, H, K, and M Cathepsin G	NK cells Neutrophils	Causative agent of NK cells, T cells	Morice et al. (2007); Zhu et al. (2009); Jahrsdorfer et al. (2010)