Structural and functional characterisation of a stable, broad-specificity multimeric sialidase from the oral pathogen Tannerella forsythia.

Sialidases are glycosyl hydrolase enzymes targeting the glycosidic bond between terminal sialic acids and underlying sugars. The NanH sialidase of Tannerella forsythia, one of the bacteria associated with severe periodontal disease plays a role in virulence. Here, we show that this broad-specificity enzyme (but higher affinity for α2,3 over α2,6 linked sialic acids) digests complex glycans but not those containing Neu5,9Ac.

Characterization of sialidase and disruption of its role in host-pathogen interactions.

Key to onset and progression of periodontitis is a complex relationship between oral bacteria and the host. The organisms most associated with severe periodontitis are the periodontal pathogens of the red complex: , and . These organisms express sialidases, which cleave sialic acid from host glycoproteins, and contribute to disease through various mechanisms.

Evidence for a carbohydrate-binding module (CBM) of NanH sialidase, key to interactions at the host-pathogen interface.

Bacterial sialidases cleave terminal sialic acid from a variety of host glycoproteins, and contribute to survival and growth of many human-dwelling bacterial species, including various pathogens. , an oral, Gram-negative, fastidious anaerobe, is a key organism in periodontal disease and possesses a dedicated sialic acid utilisation and scavenging () operon, including NanH sialidase. Here, we describe biochemical characterisation of recombinant NanH, including its action on host-relevant sialoglycans such as sialyl Lewis A and sialyl Lewis X (SLe), and on human cell-attached sialic acids directly, uncovering that it is a highly active broad specificity sialidase.