sialidaases

Sialidaases, also known as neuraminidases, are a group of enzymes that cleave sialic acids from the termini of oligosaccharides and glycoproteins. Sialic acids are a family of nine-carbon sugar derivatives found in many biological molecules, playing crucial roles in cell recognition, adhesion, and signaling. Sialidaases are essential for the metabolism of these glycoconjugates, breaking them down into simpler components.

These enzymes are found in a wide range of organisms, from bacteria and viruses to mammals. In humans, several types of sialidaases exist, encoded by different genes, each with distinct tissue distribution and substrate specificities. For example, NEU1 is primarily lysosomal, while NEU2 is cytoplasmic and NEU3 and NEU4 are membrane-associated. Dysfunctional sialidaases can lead to various inherited metabolic disorders, known as sialidases deficiencies or sialidoses, characterized by the accumulation of sialic acid-containing molecules in cells and tissues, resulting in severe neurological and physical impairments.

Viruses, particularly influenza viruses, are well-known for possessing sialidase activity. The viral neuraminidase is critical for the release of newly formed virions from infected host cells by cleaving sialic acid residues on the host cell surface, thus preventing viral aggregation and facilitating viral spread. This viral enzyme is a major target for antiviral drugs, such as oseltamivir (Tamiflu) and zanamivir (Relenza), which inhibit its activity and reduce the severity and duration of influenza infections. Bacterial sialidaases also contribute to pathogenesis by degrading host glycoconjugates, aiding in tissue invasion and nutrient acquisition.