THE MAJOR SEED PROTEINS OF THEOBROMA-CACAO L

Differential extractions of proteins from Theobroma cacao seeds have revealed the presence of an albumin fraction and a globulin fraction with proportions of 52% and 43% respectively, of total seed proteins. In contrast to some earlier reports, we could not detect any prolamin. The 'glutelin fraction' described in the literature was found to consist of residual globulin. After fermentation, the first step in cocoa processing, the proportion of the globulin fraction is considerably reduced. The major albumin is a polypeptide with an apparent molecular weight of 19 kDa. The globulin fraction contained polypeptides with apparent molecular sizes of 47 kDa, 31 kDa, and 14.5 kDa. Globulin prepared in the absence of the aspartyl protease inhibitor pepstatin contained two additional polypeptides with apparent molecular sizes of 28 kDa and 16 kDa, respectively. The negative globulin of Theobroma cacao is a glycoprotein with a sedimentation coefficient of 7-8S and a molecular weight of 150 kDa. Its subunits are not cross-linked by disulphide bridges-in contrast to the legumin-like storage globulins which are predominant in the seeds of all other dicotyledons studied so far. Therefore, Theobroma cacao is the first plant described to date whose seeds contain a vicilin-like globulin, but apparently no legumin-class globulin.