FURIN and COVID-19: Additionally, it may play a role in protecting against COVID-19 and the severity caused by this disease: on the one hand, in silico models indicate that the structure of this micronutrient can physically interact and inhibit a convertase enzyme involved in the entry of SARS-CoV-2 into the host cell (called furin) [60]; on the other hand, vitamin B9 plays a key regulatory role in the homocysteine and one-carbon metabolic pathways [61].