Presence of O-glycosidically linked oligosaccharides in the cell wall mannan of Candida krusei purified with Benanomicin A

Abstract

Cell wall mannan of the pathogenic yeast Candida krusei was prepared using the antibiotic Benanomicin A, which has a lectin-like function. The chemical structure of this molecule was found to be similar to that of mannan prepared from the same yeast by the conventional method using Fehling reagent. Only a few degradation products were detected when the mannan prepared using Fehling reagent was subjected to alkali treatment (β-elimination), but multiple α-1,2-linked oligosaccharides were detected when the mannan purified with Benanomicin A was treated with alkali. These results indicate that most of the O-linked sugar chains in mannan were lost under conventional conditions when exposed to the strongly alkaline Fehling reagent. In contrast, the O-glycosidic bond in mannan was not cleaved and the O-linked sugar chains were maintained and almost intact following treatment with the mild novel preparation method using Benanomicin A. Therefore, we argue that the new mannan preparation method using Benanomicin A is superior to conventional methods. In addition, our study suggests that some yeast mannans, whose overall structure has already been reported, may contain more O-linked sugar chains than previously recognized.

Keywords: Benanomicin A; Candida krusei; O‐linked sugar; antibiotic; cell wall mannan; β‐elimination.

Figure 1

Chemical structure of Benanomicin A.

Figure 2

Procedure of Benanomicin method (A) and Fehling method (B).

Figure 3

¹H‐NMR spectra (anomeric region) of Candida krusei mannan, Frs. K‐B (A) and K‐F (B).

Figure 4

Elution profiles of oligosaccharides obtained from Frs. K‐B (A) and K‐F (B) by the alkali treatment (β‐elimination). M4, M3, M2, and M indicate the eluted positions of standard mannooligosaccharides, tetraose, triose, biose, and mannose, respectively.

Figure 5

¹H‐NMR spectra of oligosaccharides obtained from Frs. K‐B (A) and K‐F (B) by the alkali treatment (β‐elimination). M4, M3, and M2 indicate tetraose, triose, and biose, respectively.

Figure 6

Structure of O‐linked sugar chains in the cell wall mannan of Candida krusei. Ser, Thr, Asn and M indicate serine, threonine, asparagine and mannose, respectively. *The chemical structure of N‐linked sugar chains in this mannan is not clear yet.