AIMS: The reduced fucosylation in the spike glycoprotein of SARS-CoV-2 and the IgG antibody has been observed in COVID-19 . However, the clinical relevance of & #945; -l-fucosidase, the enzyme for defucosylation has not been discovered . MATERIALS AND
METHODS : 585 COVID-19 patients were included to analyze the correlations of & #945; -l-fucosidase activity with the nucleic acid test, IgM/IgG, comorbidities, and disease progression .
RESULTS: Among the COVID-19 patients , 5.75% were double-negative for nucleic acid and antibodies . All of them had increased & #945; -l-fucosidase, while only one had abnormal serum amyloid A (SAA) and C-reactive protein (CRP). The abnormal rate of & #945; -l-fucosidase was 81.82% before the presence of IgM , 100% in the presence of IgM, and 66.2% in the presence of IgG . 73.42% of patients with glucometabolic disorders had increased & #945; -l-fucosidase activity and had the highest mortality of 6.33% . The increased & #945; -l-fucosidase was observed in 55.8% of non-severe cases and 72.9% of severe cases, with an odds ratio of 2.118 . The & #945; -l-fucosidase mRNA was irrelevant to its serum activity .
CONCLUSION: The change in & #945; -l-fucosidase activity in COVID-19 preceded the IgM and SAA and showed a preferable relation with glucometabolic disorders, which may be conducive to virus invasion or invoke an immune response against SARS-CoV-2.