Kunitz trypsin inhibitor in addition to Bowman-Birk inhibitor influence stability of lunasin against pepsin-pancreatin hydrolysis

Abstract

Soybean contains several biologically active components and one of this belongs to the bioactive peptide group. The objectives of this study were to produce different lunasin-enriched preparations (LEP) and determine the effect of Bowman-Birk inhibitor (BBI) and Kunitz trypsin inhibitor (KTI) concentrations on the stability of lunasin against pepsin-pancreatin hydrolysis (PPH). In addition, the effect of KTI mutation on lunasin stability against PPH was determined. LEP were produced by calcium and pH precipitation methods of 30% aqueous ethanol extract from defatted soybean flour. LEP, lunasin-enriched commercially available products and KTI control and mutant flours underwent PPH and samples were taken after pepsin and pepsin-pancreatin hydrolysis. The concentrations of BBI, KTI, and lunasin all decreased after hydrolysis, but they had varying results. BBI concentration ranged from 167.5 to 655.8μg/g pre-hydrolysis and 171.5 to 250.1μg/g after hydrolysis. KTI concentrations ranged from 0.3 to 122.3μg/g pre-hydrolysis and 9.0 to 18.7μg/g after hydrolysis. Lunasin concentrations ranged from 8.5 to 71.0μg/g pre-hydrolysis and 4.0 to 13.2μg/g after hydrolysis. In all products tested, lunasin concentration after PPH significantly correlated with BBI and KTI concentrations. Mutation in two KTI isoforms led to a lower concentration of lunasin after PPH. This is the first report on the potential role of KTI in lunasin stability against PPH and must be considered in designing lunasin-enriched products that could potentially survive digestion after oral ingestion.

Updating the research on the chemopreventive and therapeutic role of the peptide lunasin

“…The role of Kunitz-trypsin inhibitor on the stability of lunasin present in soybean products against pepsin-pancreatin hydrolysis has also been recently demonstrated. 42 In vivo bioavailability studies carried out in animals and humans have confirmed above in vitro findings. Hsieh et al demonstrated that lunasin was bioavailable when orally ingested by mice and rats.…”

“…These authors also studied the bioavailability of lunasin and released fragments by using Caco‐2 cell monolayers, indicating that both lunasin and fragmentRKQLQGVN were absorbed intact across the intestinal epithelium through a mechanism involving paracellular passive diffusion. The role of Kunitz–trypsin inhibitor on the stability of lunasin present in soybean products against pepsin‐pancreatin hydrolysis has also been recently demonstrated …”

Gastrointestinal Digestion of Food Proteins under the Effects of Released Bioactive Peptides on Digestive Health

“…[ 40 ] In addition to BBI, the presence of the inhibitor KTI in soybean products has been also linked to the in vitro stability of lunasin toward digestive enzymes. [ 41 ] Noteworthy, lunasin has been detected in the plasma of healthy male volunteers after intake of soybean protein (50 g during 5 days), representing a 4.5% of intestinal absorption. [ 42 ] However, studies have been mostly performed in vitro using different conditions and lunasin´s preparations, [ 38 ] hence, the study of the behavior of natural lunasin in the human GIT as well as the implementation of technologies to detect and quantify lunasin content in human samples might reveal interesting findings for the current knowledge of the bioavailability and bioactivity of this peptide.…”

Chemoprevention by means of soy proteins and peptides – current status and future approaches: a review

“…The effect of food processing on this peptide has also been demonstrated lunasin is still detectable in many commercial soybean food products such as soymilk, tofu and bean curd. Lunasin, from soybean protein extracts, partially survives the effects of digestive enzymes and food processing, and the lunasin level correlates with BBI or KTI levels, suggesting that protease inhibitors are present simultaneously with lunasin and play a protective role in wild plants (Hsieh et al ., , ; Price et al ., ).…”