Quantitative determination of active Bowman-Birk isoinhibitors, IBB1 and IBBD2, in commercial soymilks

Intestinal Exposure to Food-Derived Protease Inhibitors: Digestion Physiology- and Gut Health-Related Effects

Plant-derived protease inhibitors (PI), such as Bowman-Birk inhibitors and Kunitz-type inhibitors, have been suggested to negatively affect dietary protein digestion by blocking the activity of trypsin and chymotrypsin in the human gastrointestinal system. In addition, some PIs may possess proinflammatory activities. However, there is also scientific evidence on some beneficial effects of PIs, for example, gut-related anti-inflammatory and chemopreventive activities in vitro and in vivo. Some PIs are sensitive to processing and digestion; thus, their survival is an important aspect when considering their positive and negative bioactivities. The aim of this review was to evaluate the relevance of PIs in protein digestion in humans and to discuss the potential of PIs from whole foods and as purified compounds in decreasing symptoms of bowel-related conditions. Based on the reviewed literature, we concluded that while the complex interactions affecting plant protein digestibility and bioavailability remain unclear, PI supplements could be considered for targeted purposes to mitigate inflammation and gastric pain.

Bowman-Birk Inhibitors: Insights into Family of Multifunctional Proteins and Peptides with Potential Therapeutical Applications

Bowman-Birk inhibitors (BBIs) are found primarily in seeds of legumes and in cereal grains. These canonical inhibitors share a highly conserved nine-amino acids binding loop motif CTP1SXPPXC (where P1 is the inhibitory active site, while X stands for various amino acids). They are natural controllers of plants' endogenous proteases, but they are also inhibitors of exogenous proteases present in microbials and insects. They are considered as plants' protective agents, as their elevated levels are observed during injury, presence of pathogens, or abiotic stress, i.a. Similar properties are observed for peptides isolated from amphibians' skin containing 11-amino acids disulfide-bridged loop CWTP1SXPPXPC. They are classified as Bowman-Birk like trypsin inhibitors (BBLTIs). These inhibitors are resistant to proteolysis and not toxic, and they are reported to be beneficial in the treatment of various pathological states. In this review, we summarize up-to-date research results regarding BBIs' and BBLTIs' inhibitory activity, immunomodulatory and anti-inflammatory activity, antimicrobial and insecticidal strength, as well as chemopreventive properties.

Neutrophil elastase inhibitor purification strategy from cowpea seeds

Serine proteases and its inhibitors are involved in physiological process and its deregulation lead to various diseases like Chronic Obstructive Pulmonary Disease (COPD), pulmonary emphysema, skin diseases, atherosclerosis, coagulation diseases, cancer, inflammatory diseases, neuronal disorders and other diseases. Serine protease inhibitors have been described in many species, as well as in plants, including cowpea beans (Vigna unguiculata (L.) Walp). Here, we purified and characterized a protease inhibitor, named VuEI (Vigna unguiculata elastase inhibitor), from Vigna unguiculata, with inhibitory activity against HNE (human neutrophil elastase) and chymotrypsin but has no inhibitory activity against trypsin and thrombin. VuEI was obtained by alkaline protein extraction followed by three different chromatographic steps in sequence. First, an ion exchange chromatography using Hitrap Q column was employed, followed by two reversed-phase chromatography using Source15RPC and ACE18 columns. The molecular mass of VuEI was estimated in 10.99 kDa by MALDI-TOF mass spectrometry. The dissociation constant (Ki) to HNE was 9 pM. These data indicate that VuEI is a potent inhibitor of human neutrophil elastase, besides to inhibit chymotrypsin.

Heat-induced inactivation mechanism of soybean Bowman-Birk inhibitors

Due to the complications of the soymilk system, the heat-induced Bowman-Birk inhibitor (BBI) inactivation mechanism is not well known. In this study, two BBI samples with low and high purities were prepared from soymilk. It was confirmed that three groups (A, C, and D) of BBI, which are contained in soybean seeds, were transferred into soymilk during processing. On heating, it was found that 1) the two subdomains of BBI were not equally heat stable, 2) the conformation of BBI gradually changed, 3) some amino acid residues (namely, cystine, serine and lysine) in BBI were degraded, 4) BBI did not tend to form intermolecular cross-links with another BBI, but did slightly with non-BBI proteins. Based on some previous studies, the conformational change of BBI was attributed to β-elimination reactions on the amino acid residues of BBI and the subsequent intramolecular reactions induced by the products yielded by the β-elimination reactions.

Purification and properties of the chymotrypsin inhibitor from wild emmer wheat (Triticum dicoccoides) of Israel and its toxic effect on beet armyworm, Spodoptera exigua

A novel chymotrypsin inhibitor, which detected in the seed of wild emmer wheat (Triticum dicoccoides), was purified by ion-exchange chromatography, affinity chromatography and Ultracentrifugation. On the basis of its specificity, this inhibitor was named WeCI (wild emmer chymotrypsin inhibitor). SDS-PAGE analysis displayed that the purified WeCI is a single chain polypeptide with a molecular weight of approximately 13kDa. The inhibition constants (K_i) for amylase and bovine pancreatic chymotrypsin were 1.12×10^-9M and 2.41×10^-9M, respectively. Automated sequencing and mass spectrometry analyses revealed that WeCI is a neutral monomeric protein consisting of 119 residues. In vitro, WeCI strongly suppressed bovine pancreatic chymotrypsin as well as chymotrypsin-like activities separated from the midgut of the beet armyworm Spodoptera exigua. No inhibitory activities were found against bovine pancreatic trypsin, bacterial subtilisin, or porcine pancreatic elastase. The primary structure of WeCI was markedly similar (46-95%) to those of several proteins belonging to the wheat crop chymotrypsin/α-amylase inhibitor superfamily and displayed the typical sequence motif of the α-amylase inhibitor-seed storage protein group. WeCI significantly inhibited the growth and development of Spodoptera exigua, dependent on inhibitor concentration. WeCI significantly increased the mortality rate of Spodoptera exigua and caused a significant decrease in its fertility.

An advance for removing antinutritional protease inhibitors: Soybean whey purification of Bowman-Birk chymotrypsin inhibitor by combination of two oppositely charged polysaccharides

Two successive and selective coacervations induced by chitosan (Ch) and carrageenan (CG) were applied to remove antinutritional protease inhibitors and purify Bowman-Birk protease inhibitor (BBI) from soybean whey. At the first coacervation induced by Ch (66.7, 200, and 510kDa), only Kunitz trypsin inhibitor (KTI) and BBI complexed with Ch were extracted, while β-amylase and soybean agglutinin remained in supernatant. The binding constants for the interaction increased on the order Ch-66.7 Collapse

Key Words

• Ammonium persulfate (PubChem CID: 62648)
• BAPA (PubChem CID: 2724371)
• BTpNA (PubChem CID: 188992)
• Bicinchoninic acid (PubChem CID: 71068)
• Carrageenan
• Chitosan
• Chymotrypsin inhibitory activity
• Complex coacervation
• Coomassie Brilliant Blue G-250 (PubChem CID: 6333920)
• Dimethyl sulfoxide (PubChem CID: 679)
• N,N,N′,N′-Tetramethylethylenediamine (PubChem CID: 8037)
• Sodium dodecyl sulfate-sodium salt (PubChem CID: 3423265)
• Soybean whey proteins
• Tricine (PubChem CID: 79784)
• Trifluoroacetic acid (PubChem CID: 6422)
• Trypsin inhibitory activity

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MESH Headings

• Chymotrypsin/antagonists & inhibitors
• Polysaccharides/chemistry
• Glycine max/chemistry
• Trypsin Inhibitor, Bowman-Birk Soybean/chemistry
• Trypsin Inhibitors/chemistry

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Affiliation(s)

Xingfei Li State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu Province 214122, People's Republic of China
Yufei Hua State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu Province 214122, People's Republic of China.
Yeming Chen State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu Province 214122, People's Republic of China
Xiangzhen Kong State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu Province 214122, People's Republic of China
Caimeng Zhang State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu Province 214122, People's Republic of China
Xiaobin Yu Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, People's Republic of China

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Effects of Disulfide Bond Reduction on the Conformation and Trypsin/Chymotrypsin Inhibitor Activity of Soybean Bowman-Birk Inhibitor

Soybean seeds contain three groups (A, C, and D) of Bowman-Birk inhibitors (BBIs). In this study, highly purified BBI-A (approximately 96%) was obtained from soybean whey at the 0.1 g level by the complex coacervation method. BBI-A has seven disulfide bonds (SS) and no sulfhydryl group and exhibits trypsin inhibitor activity (TIA) and chymotrypsin inhibitor activity (CIA). The X-ray structure has shown that BBI-A has five exposed SS and two buried SS. Because of steric hindrance, it was reasonable to consider that dithiothreitol first attacks the five exposed SS and then the two buried SS, which was supported by the results that SS reduction with dithiothreitol could be divided into quick and slow stages, and the critical point was close to 5/7. The effects of SS reduction on TIA and CIA could be divided into three stages: when one exposed SS was reduced, both TIA and CIA decreased to approximately 60%; with further reduction of exposed SS, CIA gradually decreased to 8% and TIA gradually decreased to 26%; with further reduction of buried SS, CIA gradually decreased to 2% and TIA slightly decreased to 24%. Far-ultraviolet (far-UV) circular dichroism (CD) spectra showed that the secondary structure of BBI-A was slightly changed, whereas near-ultraviolet (near-UV) CD spectra showed that the conformation of BBI-A was substantially changed after the five exposed SS were reduced; further reduction of buried SS affected the conformation to some extent. The results of Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and from a C8 column showed the same trend as near-UV CD spectra. BBI-A has a structural peculiarity in that two hydrophobic patches are exposed to the exterior (in contrast to typical soluble proteins), which was attributed to the seven SS by some researchers. These results support the hypothesis that hydrophobic collapse of the exposed hydrophobic patches into a regular hydrophobic core occurred after the reduction of SS in BBI-A.

Eliminating anti-nutritional plant food proteins: the case of seed protease inhibitors in pea

Several classes of seed proteins limit the utilisation of plant proteins in human and farm animal diets, while plant foods have much to offer to the sustainable intensification of food/feed production and to human health. Reduction or removal of these proteins could greatly enhance seed protein quality and various strategies have been used to try to achieve this with limited success. We investigated whether seed protease inhibitor mutations could be exploited to enhance seed quality, availing of induced mutant and natural Pisum germplasm collections to identify mutants, whilst acquiring an understanding of the impact of mutations on activity. A mutant (TILLING) resource developed in Pisum sativum L. (pea) and a large germplasm collection representing Pisum diversity were investigated as sources of mutations that reduce or abolish the activity of the major protease inhibitor (Bowman-Birk) class of seed protein. Of three missense mutations, predicted to affect activity of the mature trypsin / chymotrypsin inhibitor TI1 protein, a C77Y substitution in the mature mutant inhibitor abolished inhibitor activity, consistent with an absolute requirement for the disulphide bond C77-C92 for function in the native inhibitor. Two further classes of mutation (S85F, E109K) resulted in less dramatic changes to isoform or overall inhibitory activity. The alternative strategy to reduce anti-nutrients, by targeted screening of Pisum germplasm, successfully identified a single accession (Pisum elatius) as a double null mutant for the two closely linked genes encoding the TI1 and TI2 seed protease inhibitors. The P. elatius mutant has extremely low seed protease inhibitory activity and introgression of the mutation into cultivated germplasm has been achieved. The study provides new insights into structure-function relationships for protease inhibitors which impact on pea seed quality. The induced and natural germplasm variants identified provide immediate potential for either halving or abolishing the corresponding inhibitory activity, along with associated molecular markers for breeding programmes. The potential for making large changes to plant protein profiles for improved and sustainable food production through diversity is illustrated. The strategy employed here to reduce anti-nutritional proteins in seeds may be extended to allergens and other seed proteins with negative nutritional effects. Additionally, the novel variants described for pea will assist future studies of the biological role and health-related properties of so-called anti-nutrients.

The protective role of the Bowman-Birk protease inhibitor in soybean lunasin digestion: the effect of released peptides on colon cancer growth

Lunasin is a naturally-occurring peptide demonstrating chemopreventive, antioxidant and anti-inflammatory properties. To exhibit these activities, orally ingested lunasin needs to survive proteolytic attack of digestive enzymes to reach target tissues in active form/s. Preliminary studies suggested the protective role of protease inhibitors, such as the Bowman-Birk inhibitor and Kunitz-trypsin inhibitor, against lunasin's digestion by both pepsin and pancreatin. This work describes in depth the behaviour of lunasin under conditions simulating the transit through the gastrointestinal tract in the absence or presence of soybean Bowman-Birk isoinhibitor 1 (IBB1) in both active and inactive states. By liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS), the remaining lunasin at the end of gastric and gastro-duodenal phases was quantified. Protection against the action of pepsin was independent of the amount of IBB1 present in the analyzed samples, whereas an IBB1 dose-dependent protective effect against trypsin and chymotrypsin was observed. Peptides released from lunasin and inactive IBB1 were identified by MS/MS. The remaining lunasin and IBB1 as well as their derived peptides could be responsible for the anti-proliferative activity against colon cancer cells observed for the digests obtained at the end of simulated gastrointestinal digestion.

Pea (Pisum sativum L.) seed albumin extracts show anti-inflammatory effect in the DSS model of mouse colitis

SCOPE

This study investigates the preventive effects of two pea (Pisum sativum) seed albumin extracts, either in the presence (pea seed extract [PSE]) or absence (albumin fraction from PSE [AF-PSE]) of soluble polysaccharides, in the dextran sodium sulfate (DSS) induced colitis in mice.

METHODS AND RESULTS

Male C57BL/6J mice were assigned to five groups: one noncolitic and four colitic. Colitis was induced by incorporating DSS (3.5%) in the drinking water for 4 days, after which DSS was removed. Treated groups received orally PSE (15 g/kg⋅day), or AF-PSE (1.5 g/kg⋅day), or pure soy Bowman-Birk inhibitor (BBI; 50 mg/kg⋅day), starting 2 wk before colitis induction, and maintained for 9 days after. All treated groups showed intestinal anti-inflammatory effect, evidenced by reduced microscopic histological damage in comparison with untreated colitic mice. The treatments ameliorated the colonic mRNA expression of different proinflammatory markers: cytokines, inducible enzymes, metalloproteinases, adhesion molecules, and toll-like receptors, as well as proteins involved in maintaining the epithelial barrier function. Furthermore, the administration of PSE, AF-PSE, or soy BBI restored bacterial counts, partially or totally, to values in healthy mice.

CONCLUSION

PSE and AF-PSE ameliorated DSS-induced damage to mice, their effects being due, at least partially, to the presence of active BBI.