Subunit structure of the vicilin-like globular storage protein of cocoa seeds and the origin of cocoa- and chocolate-specific aroma precursors
Essential cocoa-specific aroma precursors are generated during fermentation of cocoa seeds by proteolysis of the vicilin-like globulin. This particular storage protein consists of three subunits with apparent molecular masses of 47kDa, 31kDa, and 15kDa, respectively, which are derived from a common 66-kDa precursor. Since all these subunits resist N-terminal sequencing by Edman degradation, we have analysed the localisation of these vicilin subunits on their common precursor sequence by MALDI-TOF-MS analyses of their tryptic fragments. The results were corroborated by epitope mapping of polyclonal antibodies using 185 overlapping pentadeca-peptides covering the whole sequence of the precursor. The results show that the cocoa vicilin is encoded by a single gene and that heterogeneity of the vicilin subunits must be attributed to statistical post-translational modifications. Localisation of the precursor regions, from which the various subunits are derived, will be helpful for the future identification of aroma-relevant peptides generated during the fermentation process.
2009 Apr. 15, v. 113, no. 4
|Main Author:||Kratzer, Ulrich|
|Other Authors:||Frank, Ronald, Kalbacher, Hubert, Biehl, Böle, Wöstemeyer, Johannes, Voigt, Jürgen|
amino acid composition
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