Yeast mannoproteins

N. P. Arbatsky, V. N. Shibaev, and N. K. Kochetkov, A new approach to localization of the O-glycosylation sites in glycoproteins Mass-spectrometric analysis of O-glycopeptides formed upon the reductive cleavage of the yeast mannoprotein by LiBH4-LiOH, Doklady Chem., 387 (2002) 328-331. 

Caridi, A. (2006). Enological functions of parietal yeast mannoproteins. Antonie Van Leeuwenhoek, 89, 417-A22. 

Moine-Ledoux, V., and Dubourdieu, D. (2000). Role yeast mannoproteins with regard to tartaric stabilisation of wines. Bull. I O.l.V, 75, 471 82. 

Use of Yeast Mannoproteins for Stabilization of Tartrate Salt Precipitation. 149... 

Work has been done to find whether the very expensive treatment of wines with artificial cold could be advantageously replaced by the addition of inhibitors of the crystallization process of tartrate salts such as metatartaric acid, yeast mannopro-teins or carboxymethylcellulose (CMC). Such inhibitors indeed increase the width of the supersaturation field of both KHT and TCa in the wine, thus delaying tartrate salt precipitation in the bottle. Metatartaric acid is currently the product most widely used for this purpose, though its efficacy is low as this compound does not remain stable over time. Yeast mannoproteins possess stabilizing properties, which result in the spontaneous improvement of protein and tartaric salt stability, as can be... 

Other authors have searched for alternative treatments for the use of bentonites, particularly the yeast mannoproteins owing to the fact that a systematic improvement of protein stability can indeed be observed in white wines during aging on lees in barrels (Ledoux et al. 1992). Aged on lees, new wines become decreasingly... 

Besides these two systems, a new separation technique, electrodialysis, is also applied to the bitartrate stabilization of wine (Section 12.5). The use of ion-exchange resins is also permitted in certain countries, including the USA (Section 12.4.3). Finally, it is possible to prevent the precipitation of these salts by adding crystallization inhibitors, such as metatartaric acid or yeast mannoprotein extracts (Section 1.7.7), or carboxymethylcellnlose (Section 1.7.8). 

Yeast mannoproteins were first fonnd to have a certain inhibiting effect on tartrate crystallization in a model medium by Lubbers et al. (1993). However, these experiments used mannoproteins extracted by heat in alkaline buffers, under very different conditions from those accompanying the spontaneons enzymic release of mannoproteins dnring aging on the lees. Furthermore, the effectiveness of mannoproteins extracted by physical processes in preventing tartrate precipitation has not been established in most wines, despite demonstrations in a model medium. 

Arabinogalactan proteins (AGP) represented a major proportion (40%) of the total soluble polysaccharides (300 mg/1) in a red Carignan wine (Pellerin etal., 1995 Vidal etal., 2001). These macromolecules were first fractionated on a DEAF Sephacel anion exchanger, then separated from the yeast mannoproteins by affinity chromatography on Concanavaline A and finally purified, by exclusion chromatography on a Sephacryl S400 column. Table 3.4 shows the molecular characteristics of the five species obtained. 

The role of carbohydrate colloids in wine clarification and stability has been studied much more extensively. Pectic substances in wine foul filter layers (Castino and Delfini, 1984) during filtration. This phenomenon is particularly marked in tangential microfiltration (Section 11.5.2) (Feuillat and Bernard 1987 Serrano et al., 1988) as the carbohydrate colloid retention rate may be over 50%. A much higher proportion of AGPs than yeast mannoproteins is retained in this process (Brillouet et al., 1989 Belleville et al., 1990). 

AGPs also have a protective effect against protein casse in white wines (Pellerin et al., 1994 Waters et al., 1994). They are, however, less effective than yeast mannoproteins (Sections 3.7.1 and... 

The most important (and most recently demonstrated) role of yeast mannoproteins is their stabilizing effect on protein precipitation in white wine (Section 5.6.4) and tartrate crystallization (in both red and white wines) (Section 1.7.7). The most protective mannoproteins are extracted from yeast cell walls during aging on the lees. 

Grapes and wine contain many proteins with a wide range of molecular weights (30000-150000). Some unstable proteins are responsible for protein casse in white wines. Other proteins are associated with a carbohydrate fraction, e.g. yeast mannoproteins. Other proteins are associated with a carbohydrate fraction, e.g. yeast mannoproteins and isolectin, recently identified in Chardonnay must (Berthier et al.,... 

Polysaccharides are mainly extracted from the grapes at the beginning of vatting and partially precipitate in the presence of alcohol. Yeast mannoproteins may be solubilized during postfermentation maceration. 

Virginie Moine-Ledoux for her work on the use of yeast mannoproteins in preventing tartrate precipitation (Chapter 1), as well as the stabilization processes for protein casse (Chapter 5)... 

In this paper I intend to summarize what we know about yeast mannoprotein structure, what features of the biosynthetic pathway have been defined, how genetic techniques have been useful in gaining this information, and what is known about the genetic control of mannoprotein biosynthesis. 

These two developments facilitated a third namely, the elucidation of the immunochemistry of the yeast mannoproteins. 

Figure 3. Immunodominant sidechains in yeast mannoproteins. The curved lines indicate the antibody binding sites inferred from hapten inhibition studies. Refer to Figure 2 for the distribution of these determinants in different yeast mannoproteins.

---