Microbial sialidases: does bigger always mean better?

Sialidases are a superfamily of N-acylneuraminate-releasing (sialic-acid-releasing) exoglycosidases found mainly in higher eukaryotes and in some, mostly pathogenic, viruses, bacteria and protozoans. The functions of sialidases are poorly understood and, until recently, their biochemical and evolutionary relationships were unclear. A comparative approach has demonstrated the remarkable similarities and differences between nonviral sialidases, and is providing clues about their functions.