Nα-Benzoyl-DL-arginine hydrochloride

Soybean Bowman-Birk trypsin inhibitor (BBTI), an antinutritional factor of soy products, could strongly inhibit the protein digestion. The inactivation effect and mechanism of BBTI induced by tea polyphenols (TPs) and its major components (EGCG and EGC), were investigated in this study using fluorescence, FTIR, CD spectroscopy, isothermal titration calorimetry (ITC) and molecular docking. EGCG and EGC interacted with BBTI via static quenching process and hydrophobic interaction, with binding constant (Ka) of 2.19 × 103 M-1 and 0.25 × 103 M-1 at 298 K, respectively. TPs, EGCG and EGC induced a transition of BBTI conformation from disorder to order. ITC analysis and molecular docking revealed the interaction of EGCG-BBTI and EGC-BBTI were spontaneous, and hydrophobic interactions and hydrogen bonds were the predominant forces. Overall, this study clearly suggested that EGCG could be a promising inactivating agent for BBTI, which could also improve the safety and nutritional value of soy products.

An alkaline serineprotease, capable of hydrolyzing Nalpha-benzoyl- dl arginine p-nitroanilide, was secreted by Fusarium oxysporum var. lini grown in the presence of gelatin as the sole nitrogen and carbon source. The protease was purified 65-fold to electrophoretic homogenity from the culture supernatant in a three-step procedure comprising QSepharose chromatography, affinity chromatography, and FPLC on a MonoQ column. SDS-PAGE analysis of the purified protein indicated an estimated molecular mass of 41 kDa. The protease had optimum activity at a reaction temperature of 45 degrees C and showed a rapid decrease of activity at 48 degrees C. The optimum pH was around 8.0. Characterization of the protease showed that Ca2+ and Mg2+ cations increased the activity, which was not inhibited by EDTA or 1,10-phenanthroline. The enzyme activity on Nalpha-benzoyl-DL arginine p-nitroanilide was inhibited by 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride, p-aminobenzamidine dihydrochloride, aprotinin, 3-4 dichloroisocoumarin, and N-tosyl-L-lysine chloromethyl ketone. The enzyme is also inhibited by substrate concentrations higher than 2.5 x 10(-4)M. The protease had a Michaelis-Menten constant of 0.16 mM and a V(max) of 0.60 mumol released product.min(-1).mg(-1) enzyme when assayed in a non-inhibiting substrate concentration. The activity on Nalpha-benzoyl- dl arginine p-nitroanilide was competitively inhibited by p-aminobenzamidine dihydrochoride. A K(i) value of 0.04 mM was obtained.

TLC-Bioautography is a fast and effective method for assessing the inhibitory effect of compounds present in plant extracts against microbial species. However, this method has a hidden, currently underutilized potential for evaluating the presence of inhibitory compounds against selected enzymes. The aim of this work was to design a functional TLC-Bioautography method for the evaluation of protease inhibitors present in plant extracts. The method is based on the hydrolysis of Nα-benzoyl-DL-arginine-p-nitroanilide hydrochloride (BApNA) by α-chymotrypsin as a representative serine protease to produce coloured para-nitroaniline (pNA). Derivatization of pNA with both sodium nitrite and N-(1-naphthyl) ethylenediamine (NPED) leads to the formation of a pink azo dye. This step improves the resolution of active compounds on the chromatogram, which appear as light spots on a pink background. The developed method was tested for the analysis of protease inhibitors in different plant materials such as grape pomace from Vitis vinifera, Picea abies bark, Hippophae rhamnoides berries, Hordeum sativum bran, Triticum aestivum bran and Avena sativa bran. Plant extracts, which could not be analysed by a commonly used spectrophotometric method due to interference, were assessed by this method.