Subunit structure of the vicilin-like globular storage protein of cocoa seeds and the origin of cocoa- and chocolate-specific aroma precursors

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• 作者：Ulrich Kratzer ; Ronald Frank ; Hubert Kalbacher ; Bö ; le Biehl ; Johannes Wö ; stemeyer ; Jü ; rgen Voigt
• 关键词：Cocoa seeds ; Epitope mapping ; MALDI-ReTOF-MS ; Storage protein ; Theobroma cacao ; Vicilin
• 刊名：Food Chemistry
• 出版年：2009
• 出版时间：15 April 2009
• 年：2009
• 卷：113
• 期：4
• 页码：903-913
• 全文大小：2152 K

文摘

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 47 kDa, 31 kDa, and 15 kDa, 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.