Metabolic 13C-labeling of an antitumor (1-->3)-beta-D-glucan, SSG, from Sclerotinia sclerotiorum IFO 9395.

A (1-->3)-beta-D-glucan, SSG, from Sclerotinia sclerotiorum IFO 9395 was metabolically labeled using [1-13C] and [2-13C]glucose, and the fate of the 13C-label was examined by 13C-NMR spectroscopy. 13C-NMR spectra of metabolically labeled SSG (13C-SSG) showed that most of the 13C-label in glucose residues of 13C-SSG were recovered from the originally labeled sites of carbon in glucose residue, and suggested little rearrangement during take-up from the medium. In the case of poor SSG producing culture conditions (reduced shaking rate), 13C-glucose incorporation in SSG molecule was similar to that in the case of high SSG-producing culture conditions. In addition, significant amounts of 13C-labeled trehalose were found in 13C-NMR spectra of the mycelium cultured in both poor and high SSG-producing conditions. These results suggested that different culture conditions affected SSG production, but not the metabolism of glucose and the biosynthetic pathway of SSG.