Furin is a proprotein convertase enzyme in the Golgi apparatus that cleaves some proproteins into their mature forms. It may act on SARS-CoV-2 proteins during their biosynthesis based on the presence of a furin cleavage site in Spike, but its normal cellular substrates include proparathyroid hormone, transforming growth factor beta 1 precursor, proalbumin, pro-beta-secretase, membrane type-1 matrix metalloproteinase, beta subunit of pro-nerve growth factor and von Willebrand factor. It also processes precursors of HIV and other viruses, as well as some bacterial toxins. (reference:https://en.wikipedia.org/wiki/Furin).
Dear Shah Rucksana Akhter Urme thank you for your very interesting and timely question. In this context please have a look at the following relevant research articles:
1. Furin: A Potential Therapeutic Target for COVID-19
Article Furin: A Potential Therapeutic Target for COVID-19
2. A multicenter consensus: A role of furin in the endothelial tropism in obese patients with COVID-19 infection
Article A multicenter consensus: A role of Furin in the endothelial ...
Both articles are freely available as public full texts on ResearchGate.