Localization and identification of the compound causing peak ‘X’ in the 31P-NMR spectrum of Saccharomyces cerevisiae

The present study is aimed at identifying the unidentified compound which gives rise to the so-called resonance ‘X’ in the ³¹P-NMR spectra of yeast cells. In addition, it is attempted to determine the localization of X (inside or outside the cell). Enzymic removal of the cell wall causes resonance ‘X’ to disappear in the spectra of the cells. This observation indicates an extracellular localization of X. The ³¹P-NMR spectrum of the phosphomannan extracted from the yeast shows a single resonance at exactly the same position as that of resonance ‘X’. Extraction of the phosphomannan from delipidized cells causes resonance ‘X’ to disappear from the ³¹P-NMR spectrum of the cells. The intensity of resonance ‘X’ in the spectrum of the intact cells can be almost quantitatively attributed to the amount of phosphomannan present in the yeast. The present results demonstrate that the resonance ‘X’ in the ³¹P-NMR spectrum of yeast cells is caused by phosphomannan in the cell wall.