Interaction of proteins with sorghum tannin : Mechanism, specificity and significance
Butler, L.G.
Interaction of proteins with sorghum tannin : Mechanism, specificity and significance - United States of America : American Oil Chemists' Society ; John Wiley & Sons, 1984.
Peer review
The grain of some varieties of sorghum contains 2% or more condensed tannin; many other varieties contain no tannin at all. Agronomic advantages, e.g., resistance to bird depredation, are associated with high-tannin sorghums, which have relatively low nutritional value for nonruminants. The biological effects of tannin are a result of its propensity for binding proteins; both hydrogen bonding and hydrophobic interactions are involved. Sorghum tannins can bind dietary proteins and reduce their digestibility. Purified digestive enzymes are inhibited by tannin, but significant inhibition in vivo is unlikely. Proteins differ greatly in their affinity for tannin. Those with highest affinity are large, have an open structure, contain no bound carbohydrate and are rich in proline. Sorghum proteins of the alcohol-soluble prolamine fraction associate strongly with tannin, are difficult to remove during tannin purification and are found combined with tannin in the indigestible residue after in vitro digestion with pepsin. On germination, the seed may sacrifice a portion of these proteins to bind the tannin that might otherwise interfere with metabolism by inhibiting seed enzymes. During seed development, tannin molecules are relatively short and do not effectively precipitate proteins; as the seed dries, tannins undergo polymerization to an average of ca. 6 flavan-3-ol units/molecule. The antinutritional effects of sorghum tannins can be eliminated by soaking the grain in dilute aqueous alkali, but not by cooking. When rats are put on high-tannin sorghum diets, their parotid glands undergo hypertrophy and produce a group of unique salivary proteins with extremely high affinity for tannin. These proteins contain over 40% proline and are devoid of sulfur-containing and aromatic amino acids. This metabolic adaption may protect rats against tannin by binding and inactivating it immediately when it enters the digestive tract.
Text in English
0003-021X 1558-9331 (Online)
https://doi.org/10.1007/BF02542166
Interactions
Protein content
Sorghum
Tannins
Hydrophobicity
Digestibility
Carbohydrates
Interaction of proteins with sorghum tannin : Mechanism, specificity and significance - United States of America : American Oil Chemists' Society ; John Wiley & Sons, 1984.
Peer review
The grain of some varieties of sorghum contains 2% or more condensed tannin; many other varieties contain no tannin at all. Agronomic advantages, e.g., resistance to bird depredation, are associated with high-tannin sorghums, which have relatively low nutritional value for nonruminants. The biological effects of tannin are a result of its propensity for binding proteins; both hydrogen bonding and hydrophobic interactions are involved. Sorghum tannins can bind dietary proteins and reduce their digestibility. Purified digestive enzymes are inhibited by tannin, but significant inhibition in vivo is unlikely. Proteins differ greatly in their affinity for tannin. Those with highest affinity are large, have an open structure, contain no bound carbohydrate and are rich in proline. Sorghum proteins of the alcohol-soluble prolamine fraction associate strongly with tannin, are difficult to remove during tannin purification and are found combined with tannin in the indigestible residue after in vitro digestion with pepsin. On germination, the seed may sacrifice a portion of these proteins to bind the tannin that might otherwise interfere with metabolism by inhibiting seed enzymes. During seed development, tannin molecules are relatively short and do not effectively precipitate proteins; as the seed dries, tannins undergo polymerization to an average of ca. 6 flavan-3-ol units/molecule. The antinutritional effects of sorghum tannins can be eliminated by soaking the grain in dilute aqueous alkali, but not by cooking. When rats are put on high-tannin sorghum diets, their parotid glands undergo hypertrophy and produce a group of unique salivary proteins with extremely high affinity for tannin. These proteins contain over 40% proline and are devoid of sulfur-containing and aromatic amino acids. This metabolic adaption may protect rats against tannin by binding and inactivating it immediately when it enters the digestive tract.
Text in English
0003-021X 1558-9331 (Online)
https://doi.org/10.1007/BF02542166
Interactions
Protein content
Sorghum
Tannins
Hydrophobicity
Digestibility
Carbohydrates