Structural and immunochemical characterization of beta-1,2-linked mannobiosyl phosphate residue in the cell wall mannan of Candida glabrata.

A mannan of Candida glabrata IFO 0622 digested by Arthrobacter exo-alpha-mannosidase and a beta-1,2-linked mannobiose obtained from the parent mannan by acid treatment was analyzed using 13C nuclear magnetic resonance spectroscopy. The results show that the beta-1, 2-linked mannobiosyl residue is esterified to a phosphate group through position C-1 in the alpha-configuration, Manbeta1- 2Manalpha1-HPO3-. The results of immunochemical assays of these mannans using the commercial antigenic factor sera of the genus Candida (Candida Check, Iatron) indicate that the main recognition site of serum no. 6 in this kit is the mannotetraosyl side-chain Manbeta1-2Manalpha1- 2Manalpha1-2Man in C. glabrata mannan and also suggest that the phosphate-containing unit (such as Manbeta1- 2Manalpha1-HPO3- in this mannan) behaves as one of the antigenic determinants of serum no. 6, but not of serum no. 5. Therefore, the present and previous findings indicate that serum no. 5 recognizes relatively longer beta-1,2-linked oligomannosyl side-chains, Manbeta1-[2Manbeta1-]n 2Man (n = 1-6), attached to the phosphate groups previously observed in the cell wall mannans of Candida albicans, Candida stellatoidea, and Candida tropicalis.