Wall mannan of Saccharomyces cerevisiae. Metabolic stability and release into growth medium.

Selective labelling of cell wall mannan with radioactive precursors in growing Saccharomyces cerevisiae showed that this polysaccharide is metabolically stable during exponential growth. Mannan once inserted into the wall is not subject to turnover or release into the growth medium. However, about 10% of the amount of mannan incorporated into the cell wall fraction can be recovered in the non-dialyzable material isolated from the growth medium. Therefore, the mannan escaping from the cell must be either a mannan de novo synthesized, not trapped in the growing wall structure, or a mannan with a non-structural role. Radioactivity was also retained in the wall fraction of cells pre-labelled with [14C] glucose which pointed to metabolic stability of all cell wall polysaccharides in growing S. cerevisiae.