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 α-(1⃗3), α-(1⃗6) and β-(1⃗4) 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 α-(1⃗2) mannosidase which is required to initiate breakdown of the glycan chains present in the other glycoforms which are components of the glycoprotein.