ATP5MK and viral infectious disease: Analysis of both serum AGP concentrations and the profile and degree of its N-glycosylation, supplemented by measurement of the redox potential in the sera of patients with severe COVID-19, convalescents, and healthy individuals who were not infected with SARS-CoV-2 before the study, may contribute to a deeper understanding of the molecular mechanisms underlying the development of many inflammatory diseases, including viral diseases such as COVID-19, and provide a basis for proposing new biomarkers with potential diagnostic applications.