Glucan synthesis in Pneumocystis carinii.

Rat-derived Pneumocystis carinii lysed with sodium deoxycholate catalysed the incorporation of uridine diphosphoglucose into an insoluble polymer. This enzyme activity was present in both the pellet and the supernatant when the P. carinii preparations were centrifuged. The polymer whose production was catalysed by the supernatant was examined by mass spectrometry and found to be an alpha-1 --> 4 glucan, which is either unbranched or has relatively few branches. Polymer formation was completely inhibited by the addition of alpha-amyloglucohydrolase to the supernatant. Polymer formation in the pellet of deoxycholate P. carinii preparations, unlike that in the supernatant, was partially resistant to alpha-amyloglucohydrolase. The soluble glucan synthase activity in the supernatant was stable for more than 30 h at room temperature and was approximately 50 times more active on a cell-to-cell basis than the supernatant from deoxycholate preparations of the yeast Saccharomyces cerevisiae.