ACE-2-like enzymatic activity is associated with immunoglobulin in COVID-19 patients

Abstract

AbstractMany mechanisms responsible for COVID-19 pathogenesis are well-established, but COVID-19 includes features with unclear pathogenesis, such as autonomic dysregulation, coagulopathies, and high levels of inflammation. The receptor for SARS-CoV-2 spike protein’s receptor binding domain (RBD) is angiotensin converting enzyme 2 (ACE2). We hypothesized that some COVID-19 patients may develop antibodies that have negative molecular image of RBD sufficiently similar to ACE2 to yield ACE2-like catalytic activity – ACE2-like abzymes. To explore this hypothesis, we studied patients hospitalized with COVID-19 who had plasma samples available obtained about 7 days after admission. ACE2 is a metalloprotease that requires Zn2+for activity. However, we found that the plasma from some patients studied could cleave a synthetic ACE2 peptide substrate, even though the plasma samples were collected using disodium ethylenediaminetetraacetate (EDTA) anticoagulant. When we spiked plasma with synthetic ACE2, no ACE2 substrate cleavage activity was observed unless Zn2+was added or the plasma was diluted to decrease EDTA concentration. After processing samples by 100 kDa size exclusion columns and protein A/G adsorption, which depleted immunoglobulin by >99.99%, the plasma samples did not cleave the ACE2 substrate peptide. The data suggest that some patients with COVID-19 develop antibodies with abzyme-like activity capable of cleaving synthetic ACE2 substrate. Since abzymes can exhibit promiscuous substrate specificities compared to the enzyme whose active site image they resemble, and since proteolytic cascades regulate many physiologic processes, anti-RBD abzymes may contribute to some otherwise obscure COVID-19 pathogenesis.