This HE enzyme is present in the envelope of CoV, more specifically among beta-coronaviridiae.[86] The HE is a marker of CoV and influenza virus evolution.[86] HE mediates reversible attachment to O-acetylated-sialic-acids by acting both as lectins and as receptor-destroying enzymes.[86] Interactions between HE in complex with sialic acid can be visualized in PDB ID: 3CL5.[86]