Evidence for mannosidase activities in Streptococcus oralis when grown on glycoproteins as carbohydrate source.

Streptococcus oralis when cultured using ribonuclease B as the sole source of carbohydrate, selectively uses the sugars of the Man5 glycoform as shown by HPAEC and MALDI-TOF mass spectrometric analyses. The organism is able to do this by producing novel alpha-(1-->3), alpha-(1-->6) and beta-(1-->4) mannosidase activities and these act in a concerted manner in what appears as a single-step process. The selective utilisation of Man5 is explained by the absence of an alpha-(1-->2) mannosidase which is required to initiate breakdown of the glycan chains present in the other glycoforms which are components of the glycoprotein.