Limits...
Susceptibility of sweet potato (Ipomoea batatas) peel proteins to digestive enzymes.

Maloney KP, Truong VD, Allen JC - Food Sci Nutr (2014)

Bottom Line: The ability of a protein to exhibit systemic effects is somewhat unusual as proteins are typically susceptible to digestive enzymes.Trypsin inhibitory activity remained after simulated gastric digestion, with the Caiapo potato protein and peel samples exhibiting higher inhibitory activity compared to the blanched peel sample.Amylase and chymotrypsin inhibitory activity was not present in any of the samples after digestion.

View Article: PubMed Central - PubMed

Affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University Raleigh, North Carolina.

ABSTRACT
Sweet potato proteins have been shown to possess antioxidant and antidiabetic properties in vivo. The ability of a protein to exhibit systemic effects is somewhat unusual as proteins are typically susceptible to digestive enzymes. This study was undertaken to better understand how digestive enzymes affect sweet potato proteins. Two fractions of industrially processed sweet potato peel, containing 6.8% and 8.5% protein and 80.5% and 83.3% carbohydrate, were used as a source of protein. Sweet potato proteins were incubated with pepsin, trypsin, and chymotrypsin and protein breakdown was visualized with SDS-PAGE. After pepsin digestion, samples were assayed for amylase inhibitory activity. Sporamin, the major storage protein in sweet potatoes, which functions as a trypsin inhibitor as well, exhibited resistance to pepsin, trypsin, and chymotrypsin. Sporamin from blanched peel of orange sweet potatoes was less resistant to pepsin digestion than sporamin from outer peel and from extract of the white-skinned Caiapo sweet potato. Trypsin inhibitory activity remained after simulated gastric digestion, with the Caiapo potato protein and peel samples exhibiting higher inhibitory activity compared to the blanched peel sample. Amylase and chymotrypsin inhibitory activity was not present in any of the samples after digestion.

No MeSH data available.


Related in: MedlinePlus

Theoretical (A) pepsin, (B) trypsin, or (C) chymotrypsin, cleavage sites of sporamin determined by inputting sporamin protein sequence from GenBank accession AAB52550 into ExPASy PeptideCutter. Likelihood of cleavage is shown in parenthesis. Only sites with a likelihood of cleavage greater than 50% are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4221833&req=5

fig04: Theoretical (A) pepsin, (B) trypsin, or (C) chymotrypsin, cleavage sites of sporamin determined by inputting sporamin protein sequence from GenBank accession AAB52550 into ExPASy PeptideCutter. Likelihood of cleavage is shown in parenthesis. Only sites with a likelihood of cleavage greater than 50% are shown.

Mentions: Visualization of proteins with SDS-PAGE at various points during digestion of Caiapo, peel extract, and blanched peel extract with pepsin, trypsin, and chymotrypsin revealed that sporamin exhibits resistance to cleavage by these enzymes. Our control protein, bovine serum albumin, on the other hand, was hydrolyzed after 1 min of incubation under the conditions of the assay (data not shown). The density of the sporamin band in Caiapo and peel extract remained unchanged despite incubation with pepsin, trypsin, and chymotrypsin (Figs. 1, 2). The density of the sporamin band in blanched peel extract decreased as incubation time increased, however, resistance to digestive enzymes was still noted (Fig. 3). After 1 min of incubation with pepsin, sporamin band density in the blanched peel sample decreased to 55% of the original band density. After 60 min, the band density decreased to 23% of the original density. The sporamin that remained after 60 min of incubation with pepsin was resistant to digestion by trypsin and chymotrypsin, indicated by the lack of difference between the sporamin band density at the start of incubation and after 60 min of incubation. Protein resistance to digestion might be due to either a unique amino acid sequence that hinders the ability of digestive enzymes to recognize cleavage sites, or compact structure, which hinders the ability of the digestive enzymes to reach the cleavage sites. The computer program ExPASy PeptideCutter was used to predict potential cleavage sites on sporamin for pepsin, trypsin, and chymotrypsin, in order to determine if resistance was due to a unique amino acid sequence. The sequence used for sporamin was GenBank accession AAB52550, determined by Yeh et al. (1997). Sporamin contained numerous potential cleavage sites for pepsin, trypsin, and chymotrypsin (Fig. 4, A–C), indicating that a unique amino acid sequence is not likely the mechanism for the resistance of sporamin to digestion. The compact structure of the protein is more likely responsible for the lack of cleavage by digestive enzymes. Sugiura et al. (1973) found that sweet potato trypsin inhibitors with molecular weights of 23 and 24 kDa (probably sporamin) were stable at pH = 2 and 37°C. As this is within the pH range and temperature of the stomach, it is likely that potential cleavage sites were inaccessible to pepsin due to the structural stability of sporamin. Compact structure has been found to play a role in reducing the digestibility of several proteins, including chickpea albumin (Clemente et al. 2000), lupin γ-conglutin (Capraro et al. 2009), and many allergenic albumins (Moreno and Clemente 2008).


Susceptibility of sweet potato (Ipomoea batatas) peel proteins to digestive enzymes.

Maloney KP, Truong VD, Allen JC - Food Sci Nutr (2014)

Theoretical (A) pepsin, (B) trypsin, or (C) chymotrypsin, cleavage sites of sporamin determined by inputting sporamin protein sequence from GenBank accession AAB52550 into ExPASy PeptideCutter. Likelihood of cleavage is shown in parenthesis. Only sites with a likelihood of cleavage greater than 50% are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4221833&req=5

fig04: Theoretical (A) pepsin, (B) trypsin, or (C) chymotrypsin, cleavage sites of sporamin determined by inputting sporamin protein sequence from GenBank accession AAB52550 into ExPASy PeptideCutter. Likelihood of cleavage is shown in parenthesis. Only sites with a likelihood of cleavage greater than 50% are shown.
Mentions: Visualization of proteins with SDS-PAGE at various points during digestion of Caiapo, peel extract, and blanched peel extract with pepsin, trypsin, and chymotrypsin revealed that sporamin exhibits resistance to cleavage by these enzymes. Our control protein, bovine serum albumin, on the other hand, was hydrolyzed after 1 min of incubation under the conditions of the assay (data not shown). The density of the sporamin band in Caiapo and peel extract remained unchanged despite incubation with pepsin, trypsin, and chymotrypsin (Figs. 1, 2). The density of the sporamin band in blanched peel extract decreased as incubation time increased, however, resistance to digestive enzymes was still noted (Fig. 3). After 1 min of incubation with pepsin, sporamin band density in the blanched peel sample decreased to 55% of the original band density. After 60 min, the band density decreased to 23% of the original density. The sporamin that remained after 60 min of incubation with pepsin was resistant to digestion by trypsin and chymotrypsin, indicated by the lack of difference between the sporamin band density at the start of incubation and after 60 min of incubation. Protein resistance to digestion might be due to either a unique amino acid sequence that hinders the ability of digestive enzymes to recognize cleavage sites, or compact structure, which hinders the ability of the digestive enzymes to reach the cleavage sites. The computer program ExPASy PeptideCutter was used to predict potential cleavage sites on sporamin for pepsin, trypsin, and chymotrypsin, in order to determine if resistance was due to a unique amino acid sequence. The sequence used for sporamin was GenBank accession AAB52550, determined by Yeh et al. (1997). Sporamin contained numerous potential cleavage sites for pepsin, trypsin, and chymotrypsin (Fig. 4, A–C), indicating that a unique amino acid sequence is not likely the mechanism for the resistance of sporamin to digestion. The compact structure of the protein is more likely responsible for the lack of cleavage by digestive enzymes. Sugiura et al. (1973) found that sweet potato trypsin inhibitors with molecular weights of 23 and 24 kDa (probably sporamin) were stable at pH = 2 and 37°C. As this is within the pH range and temperature of the stomach, it is likely that potential cleavage sites were inaccessible to pepsin due to the structural stability of sporamin. Compact structure has been found to play a role in reducing the digestibility of several proteins, including chickpea albumin (Clemente et al. 2000), lupin γ-conglutin (Capraro et al. 2009), and many allergenic albumins (Moreno and Clemente 2008).

Bottom Line: The ability of a protein to exhibit systemic effects is somewhat unusual as proteins are typically susceptible to digestive enzymes.Trypsin inhibitory activity remained after simulated gastric digestion, with the Caiapo potato protein and peel samples exhibiting higher inhibitory activity compared to the blanched peel sample.Amylase and chymotrypsin inhibitory activity was not present in any of the samples after digestion.

View Article: PubMed Central - PubMed

Affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University Raleigh, North Carolina.

ABSTRACT
Sweet potato proteins have been shown to possess antioxidant and antidiabetic properties in vivo. The ability of a protein to exhibit systemic effects is somewhat unusual as proteins are typically susceptible to digestive enzymes. This study was undertaken to better understand how digestive enzymes affect sweet potato proteins. Two fractions of industrially processed sweet potato peel, containing 6.8% and 8.5% protein and 80.5% and 83.3% carbohydrate, were used as a source of protein. Sweet potato proteins were incubated with pepsin, trypsin, and chymotrypsin and protein breakdown was visualized with SDS-PAGE. After pepsin digestion, samples were assayed for amylase inhibitory activity. Sporamin, the major storage protein in sweet potatoes, which functions as a trypsin inhibitor as well, exhibited resistance to pepsin, trypsin, and chymotrypsin. Sporamin from blanched peel of orange sweet potatoes was less resistant to pepsin digestion than sporamin from outer peel and from extract of the white-skinned Caiapo sweet potato. Trypsin inhibitory activity remained after simulated gastric digestion, with the Caiapo potato protein and peel samples exhibiting higher inhibitory activity compared to the blanched peel sample. Amylase and chymotrypsin inhibitory activity was not present in any of the samples after digestion.

No MeSH data available.


Related in: MedlinePlus