Abstract
The interest in extracting kafirins (KAF), the main storage protein from sorghum grain has recently increased due to its gluten-free content and the significant scientific evidence showing the health benefits of the bioactive peptides from cereal grains in human diets. The objectives were to obtain the highest percentage of KAF extraction using amyloglucosidase as pretreatment to increase the extraction yield and predict the bioactive peptides in the KAF. In this study, pretreatments with amyloglucosidase increased the extraction yield of KAF compared with extraction methods using only ethanol and sodium metabisulfite. Two protein fragment sequences were identified from KAF extract and were evaluated for potential bioactive peptide using the BIOPEP-UWM database, which suggest that KAF proteins from white sorghum may be considered as good precursors of dipeptidyl peptidase-inhibitor, angiotensin-converting enzyme inhibitor, antioxidant and hypotensive peptides following chymotrypsin, thermolysin, and subtilisin and their combination. Average scores aligned using PeptideRanker confirmed KAF proteins' potential sources of bioactive peptides with over 5 peptides scored over 0.8. In addition, 31 unexplored peptide sequences that could have biological activity were identified. Our results suggest that KAF can be used in the peptide productions with potential biological activity and beyond.
Highlights
IntroductionSorghum grain represents an average of 11% protein, which are classified into albumins, globulins, and glutelins accounting for 30% and prolamins, called kafirins (KAF) for the sorghum grain, represent 70–80% of the total protein.[1,3] KAF are classified as a-KAF (25– 23 kDa), b-KAF (20–16 kDa), c-KAF (28–50 kDa), and d-KAF (13 kDa) and are located in the endosperm, forming agglomerations and interacting with the glutelin matrix and distributed around the starch granules, which makes it difficult to extract KAF.[2,3,4,5,6] The most applied extraction protocol to recover KAF is the use of ethanol and sodium metabisulfite as reducing agent,[7,8] detailed information on suitable extraction methods of KAF using enzymatic pretreatments are limited
Two protein fragment sequences were identified from KAF extract and were evaluated for potential bioactive peptide using the BIOPEP-UWM database, which suggest that KAF proteins from white sorghum may be considered as good precursors of dipeptidyl peptidase-inhibitor, angiotensin-converting enzyme inhibitor, antioxidant and hypotensive peptides following chymotrypsin, thermolysin, and subtilisin and their combination
Sorghum grain represents an average of 11% protein, which are classified into albumins, globulins, and glutelins accounting for 30% and prolamins, called kafirins (KAF) for the sorghum grain, represent 70–80% of the total protein.[1,3]
Summary
Sorghum grain represents an average of 11% protein, which are classified into albumins, globulins, and glutelins accounting for 30% and prolamins, called kafirins (KAF) for the sorghum grain, represent 70–80% of the total protein.[1,3] KAF are classified as a-KAF (25– 23 kDa), b-KAF (20–16 kDa), c-KAF (28–50 kDa), and d-KAF (13 kDa) and are located in the endosperm, forming agglomerations and interacting with the glutelin matrix and distributed around the starch granules, which makes it difficult to extract KAF.[2,3,4,5,6] The most applied extraction protocol to recover KAF is the use of ethanol and sodium metabisulfite as reducing agent,[7,8] detailed information on suitable extraction methods of KAF using enzymatic pretreatments are limited
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