Amino acid sequence of chymotrypsin inhibitor ECI from the seeds of Erythrina variegata (Linn.) var. Orientalis

Contribution of Conserved Asn Residues to the Inhibitory Activities of Kunitz-Type Protease Inhibitors from Plants

Plant Kunitz-type protease inhibitors contain a conserved Asn residue in the N-terminal region. To investigate the role of Asn residue in protease inhibitory activities, Erythrina variegata trypsin inhibitor a (ETIa), E. variegata chymotrypsin inhibitor (ECI), and their mutants, ETIa-N12A and ECI-N13A, were used. Both mutants exhibit weaker inhibitory activities toward their cognate proteases than the wild-type proteins and were readily cleaved at reactive sites. Furthermore, kinetic analysis of the interactions of the mutated proteins with their cognate proteases by surface plasmon resonance (SPR) measurement indicated that replacements of the Asn residue mainly affected dissociation rate constants. The conserved Asn residues of Kunitz-type inhibitors play an important role in exhibiting effective inhibitory activity by stabilizing the structures of the primary binding loop and protease-inhibitor complex.

Characterization and pharmacological properties of a novel multifunctional Kunitz inhibitor from Erythrina velutina seeds

Inhibitors of peptidases isolated from leguminous seeds have been studied for their pharmacological properties. The present study focused on purification, biochemical characterization and anti-inflammatory and anticoagulant evaluation of a novel Kunitz trypsin inhibitor from Erythrina velutina seeds (EvTI). Trypsin inhibitors were purified by ammonium sulfate (30-60%), fractionation followed by Trypsin-Sepharose affinity chromatography and reversed-phase high performance liquid chromatography. The purified inhibitor showed molecular mass of 19,210.48 Da. Furthermore, a second isoform with 19,228.16 Da was also observed. The inhibitor that showed highest trypsin specificity and enhanced recovery yield was named EvTI (P2) and was selected for further analysis. The EvTI peptide fragments, generated by trypsin and pepsin digestion, were further analyzed by MALDI-ToF-ToF mass spectrometry, allowing a partial primary structure elucidation. EvTI exhibited inhibitory activity against trypsin with IC50 of 2.2×10(-8) mol.L(-1) and constant inhibition (Ki) of 1.0×10(-8) mol.L(-1), by a non-competitive mechanism. In addition to inhibit the activity of trypsin, EvTI also inhibited factor Xa and neutrophil elastase, but do not inhibit thrombin, chymotrypsin or peptidase 3. EvTI was investigated for its anti-inflammatory and anti-coagulant properties. Firstly, EvTI showed no cytotoxic effect on human peripheral blood cells. Nevertheless, the inhibitor was able to prolong the clotting time in a dose-dependent manner by using in vitro and in vivo models. Due to anti-inflammatory and anticoagulant EvTI properties, two sepsis models were here challenged. EvTI inhibited leukocyte migration and specifically acted by inhibiting TNF-α release and stimulating IFN-α and IL-12 synthesis. The data presented clearly contribute to a better understanding of the use of Kunitz inhibitors in sepsis as a bioactive agent capable of interfering in blood coagulation and inflammation.

Inhibitory effects of a Kunitz-type inhibitor from Pithecellobium dumosum (Benth) seeds against insect-pests' digestive proteinases

Pithecellobium dumosum is a tree belonging to the Mimosoideae subfamily that presents various previously characterized Kunitz-type inhibitors. The present study provides a novel Kunitz-trypsin inhibitor isoform purified from P. dumosum seeds. Purification procedure was performed by TCA precipitation followed by a trypsin-Sepharose chromatography and a further reversed-phase HPLC. Purified inhibitor (PdKI-4) showed enhanced inhibitory activity against bovine trypsin and chymotrypsin. Furthermore, PdKI-4 showed remarkable inhibitory activity against serine proteases from the coleopterans Callosobruchus maculatus and Zabrotes subfasciatus, and the lepidopterans Alabama argillacea and Telchin licus. However, PdKI-4 was unable to inhibit porcine pancreatic elastase, pineapple bromelain and Carica papaya papain. SDS-PAGE showed that PdKI-4 consisted of a single polypeptide chain with molecular mass of 21 kDa. Kinetic studies demonstrated that PdKI-4 is probably a competitive inhibitor with a Ki value of 5.7 × 10(-10) M for bovine trypsin. PdKI-4 also showed higher stability over a wide range of temperature (37-100 °C) and pH (2-12). N-termini sequence was obtained by Edman degradation showing higher identity with other Mimosoideae subfamily Kunitz-type inhibitor members. In summary, data here reported indicate the biotechnological potential of PdKI-4 for development of products against insect-pests.

Trypsin inhibitor from Poecilanthe parviflora seeds: purification, characterization, and activity against pest proteases

Plants synthesize a variety of molecules, including proteinaceous proteinase inhibitors, to defend themselves of being attacked by insects. In this work, a novel trypsin inhibitor (PPTI) was purified from the seeds of the native Brazilian tree Poecilanthe parviflora (Benth) (Papilioinodeae, Leguminosae) by gel filtration chromatography on a Sephadex G-100 followed by Superdex G75 chromatography (FPLC), Sepharose 4B-Trypsin column, and fractionated by reversed-phase HPLC on a C-18 column. SDS-PAGE showed that PPTI consisted of a single polypeptide chain with molecular mass of about 16 kDa. The dissociation constant of 1.0 x 10(-7) M was obtained with bovine trypsin. PPTI was stable over a wide range of temperature and pH and in the presence of DTT. The N-terminal sequence of the PPTI showed a high degree of homology with other Kunitz-type inhibitors. Trypsin-like activity in midguts of larval Diatraea saccharalis, Anagasta kuehniella, Spodoptera frugiperda, and Corcyra cephalonica were substantially inhibited by PPTI.

Pyroglutamic acid in cheese: presence, origin, and correlation with ripening time of Grana Padano cheese

Pyroglutamic acid is present in many cheese varieties and particularly in high amounts (0.5 g/100 g of cheese) in extensively ripened Italian cheeses (Grana Padano and Parmigiano Reggiano) that are produced with thermophilic lactic acid bacteria as starters. The mechanism of pyroglutamic acid formation in cheese seems to be mostly enzymatic, as demonstrated by the presence of only L-pyroglutamic acid enantiomer. Thermophilic lactobacilli are involved in pyroglutamic acid production, as suggested by the low pyroglutamic acid content found in Bagos, a ripened Italian mountain cheese produced without addition of starter. Because milk pasteurization did not influence the pyroglutamic acid content in the ripened Grana Padano cheese, the formation of pyroglutamic acid mainly depends on the whey starter microflora rather than that of raw milk. Pyroglutamic acid concentration is linearly correlated (R2 = 0.94) with the age of Grana Padano cheese.

Analysis of the complex formed by Erythrina variegata chymotrypsin inhibitor with chymotrypsin and properties of the peptides prepared from the inhibitor by a limited proteolysis

The stoichiometry of Erythrina variegata chymotrypsin inhibitor (ECI) and chymotrypsin interaction was previously estimated to be 1:2 by a titration of inhibitory activity. In the present study, gel-permeation chromatography and reverse-phase HPLC (RP-HPLC) were employed to analyze the complex formed by the inhibitor and enzyme. The results showed that ECI and chymotrypsin molecules undergo aggregation in the complex-forming buffer simultaneously with a binary complex consisting of one ECI and one chymotrypsin molecules in a soluble form. A mild lysylendopeptidase digestion of ECI produced two peptides in high yield, which were separated by RP-HPLC and characterized in terms of their structures and inhibitory activities. The N-terminal peptide, ECI-(1-107)-peptide, containing the primary reactive site retained a slight inhibitory activity, while the C-terminal peptide, ECI-(108-179)-peptide, exhibited no inhibitory activity. The inhibitory potency of the ECI-(1-107)-peptide was enhanced by the presence of the ECI-(108-179)-peptide in reconstituted mixture. Recovery of the native-like structure of the reconstituted complex was further indicated by fluorescence spectra, which showed strong conformational interaction between the two peptides; their dissociation constant Kd was calculated to be 209 nM. Taken together with the previous result obtained by chymotryptic digestion, it is suggested that the primary binding loop in ECI interacts with chymotrypsin not only by a standard mechanism but also by a non-substrate-like manner. Alternatively, ECI might have an additional binding segment in the N-terminal region which interacts with chymotrypsin by a non-substrate-like manner. Further, it is shown that the C-terminal region may support the native conformation of the binding loop(s) in the N-terminal region as an intramolecular chaperone.

Major proteins of yam bean tubers

The tuberous roots of the Mexican yam bean, jicama, (Pachyrhizus erosus L. Urban) contained large quantities of two acidic glycoproteins which accounted for more than 70% of the total soluble proteins (about 3 g per 100 g of tuber on a dry weight basis). The two major proteins, tentatively named YBG1 and YBG2, had apparent M(r)s of 28,000 and 26,000, respectively, by SDS-PAGE. A third protein named YBP22 which accounted for 2-5% of the total soluble proteins had an M(r) of 22,000. YBG1 and YBG2 exhibited great similarity on the basis of their amino acid composition and had identical N-terminal amino acid sequences. The first 23 amino acids in the N-terminal region of YBG2 were DDLPDYVDWRDYGAVTRIKNQGQ which showed strong homology with the papain class of cysteine proteases. YBG1 and YBG2 were found to bind to a Concanavalin A-Sepharose column and were also stained positively by a sensitive glycoprotein stain. Both glycoproteins exhibited cysteine proteolytic activity. In contrast, YBP22 showed sequence homology with several known protease inhibitors, and a polyclonal antibody raised against this protein cross reacted with soybean trypsin inhibitor.

A wound-inducible gene from Salix viminalis coding for a trypsin inhibitor

A gene designated swin1.1 has been isolated by screening a Salix viminalis genomic library with a heterologous probe, win3 from Populus. The region sequenced included the entire coding sequence for a protein with 199 amino acids plus the promoter and terminator. At the 5' end of the coding region is a sequence that encodes a hydrophobic region of 25-30 amino acids, that could form a signal peptide. A putative TATAA box and polyadenylator sequence were identified. Introns were absent. The gene product showed similarities with serine protease inhibitors from the Kunitz family and especially with win3 from wounded leaves of Populus. Southern blot analysis indicated that swin1.1 is a member of a clustered gene family, swin1. An oligonucleotide corresponding to the putative hypervariable region towards the carboxyl end when used as a probe in Southern hybridization showed high specificity for swin1.1. Expression of the swin1.1 gene was enhanced in wounded leaves. The swin1.1 coding region without the signal sequence was highly expressed in Escherichia coli and the protein showed inhibitory activity against trypsin but at most slight activity against the other proteases tested. A systemically induced protein, SVTI, with inhibitor activity against trypsin, was isolated from Salix leaves by affinity chromatography on a column of trypsin-Sepharose 4B and N-terminal sequenced. It corresponded with the translated swin1.1 gene at 16 of the 19 amino acid sites, suggesting that SVTI is encoded by another member of the swin1 gene family.