Purification of a Kunitz-type inhibitor from Acacia polyphyllaDC seeds: characterization and insecticidal properties against Anagasta kuehniella Zeller (Lepidoptera: Pyralidae)

A Novel Kunitz Trypsin Inhibitor from Enterolobium gummiferum Seeds Exhibits Antibiofilm Properties against Pathogenic Yeasts

Plant peptidase inhibitors play crucial roles in plant defence mechanisms and physiological processes. In this study, we isolated and characterised a Kunitz trypsin inhibitor from Enterolobium gummiferum seeds named EgPI (E. gummiferum peptidase inhibitor). The purification process involved two chromatography steps using size exclusion and hydrophobic resins, resulting in high purity and yield. EgPI appeared as a single band of ~20 kDa in SDS-PAGE. Under reducing conditions, the inhibitor exhibited two polypeptide chains, with 15 and 5 kDa. Functional characterisation revealed that EgPI displayed an inhibition stoichiometry of 1:1 against trypsin, with a dissociation constant of 8.4 × 10-9 mol·L-1. The amino-terminal sequencing of EgPI revealed the homology with Kunitz inhibitors. Circular dichroism analysis provided insights into the secondary structure of EgPI, which displayed the signature typical of Kunitz inhibitors. Stability studies demonstrated that EgPI maintained the secondary structure necessary to exhibit its inhibitory activity up to 70 °C and over a pH range from 2 to 8. Microbiological screening revealed that EgPI has antibiofilm properties against pathogenic yeasts at 1.125 μmol·L-1, and EgPI reduced C. albicans biofilm formation by 82.7%. The high affinity of EgPI for trypsin suggests potential applications in various fields. Furthermore, its antibiofilm properties recommended its usefulness in agriculture and antimicrobial therapy research, highlighting the practical implications of our research.

Structural and functional relationship of Cassia obtusifolia trypsin inhibitor to understand its digestive resistance against Pieris rapae

Although digestive resistance of Kunitz protease inhibitors has been reported extensively, the molecular mechanism is not well established. In the present study, the first X-ray structure of Cassia obtusifolia trypsin inhibitor (COTI), a member of Kunitz protease inhibitors, was solved at a resolution of 1.9 Å. The structure adopted a classic β-trefoil fold with the inhibitory loop protruding from the hydrophobic core. The role of Phe139, a unique residue in Kunitz protease inhibitors, and Arg63 in the COTI structure was verified by F139A and R63E mutants. COTI was a specific inhibitor of bovine trypsin and the result was also verified by COTI-trypsin complex formation. Meanwhile, COTI showed equivalent inhibitory activity with that of soybean trypsin inhibitor against bovine trypsin and midgut trypsin from Pieris rapae. The F139 and R63E mutants further indicated that inhibitory specificity and efficiency of COTI were closely related to the global framework, the conformation and the amino acid composition of reactive loop. Finally, a midgut trypsin from P. rapae (PrSP40), which might be involve in the food digestion, was proposed to be a potential target of COTI and might be a promising target for future crop-protection strategy. The results supported the digestive resistance of COTI.

Exploration of anti-insect potential of trypsin inhibitor purified from seeds of Sapindus mukorossi against Bactrocera cucurbitae

Peptidase inhibitors (PIs) are defense proteins of plants which are active against gut peptidases of different insects. Sapindus mukorossi was identified as a source of bioactive PIs which could confer resistance against Bactrocera cucurbitae, a most devastating pest of several economically important crops. In the present study, a trypsin inhibitor was purified from mature dry seeds of S. mukorossi and characterized for its biochemical properties as well as its potential for bio control of B. cucurbitae. The purified fractions from RP- HPLC through SDS-PAGE gave an apparent molecular weight of ~29 kDa. S. mukorossi trypsin inhibitor (SMTI) was found to be a non-competitive inhibitor which was active over a broad range of temperature (10–100 °C) and pH (6–11). SMTI when incorporated in artificial diet inhibited the growth and development of B. cucurbitae larvae. Gene expression analysis of trypsin and chymotrypsin genes via qRT-PCR indicated that their mRNA expression was down-regulated while that of other genes namely, Catalase, Elastase, Superoxide Dismutase, Glutathione –S-transferase and Alkaline Phosphatase was up regulated. SMTI also showed deleterious effects against different bacterial strains. The results of this study indicated that S. mukorossi trypsin inhibitor has potential to be used as a bio control agent that can reduce the harm caused by melon fruit fly and other devastating pests.

The effects of Enterolobium contortisiliquum serine protease inhibitor on the survival of the termite Nasutitermes corniger, and its use as affinity adsorbent to purify termite proteases

The immobilization of Enterolobium contortisiliquum protease inhibitor, EcTI-Sepharose, as an affinity chromatography matrix is a powerful biotechnological tool to purify targets from Nasutitermes corniger in the investigation of insecticidal properties of natural compounds.

Novel Peptidase Kunitz Inhibitor from Platypodium elegans Seeds Is Active against Spodoptera frugiperda Larvae

A novel Kunitz-type inhibitor from Platypodium elegans seeds (PeTI) was purified and characterized. The mass spectrometry analyses of PeTI indicated an intact mass of 19 701 Da and a partial sequence homologous to Kunitz inhibitors. PeTI was purified by ion exchange and affinity chromatographies. A complex with a 1:1 ratio was obtained only for bovine trypsin, showing a K_i = 0.16 nM. Stability studies showed that PeTI was stable over a wide range of temperature (37-80 °C) and pH (2-10). The inhibitory activity of PeTI was affected by dithiothreitol (DTT). Bioassays of PeTI on Spodoptera frugiperda showed negative effects on larval development and weight gain, besides extending the insect life cycle. The activities of digestive enzymes, trypsin and chymotrypsin, were reduced by feeding larvae with 0.2% PeTI in an artificial diet. In summary, we describe a novel Kunitz inhibitor with promising biotechnological potential for pest control.

Bowman-Birk proteinase inhibitor from Clitoria fairchildiana seeds: Isolation, biochemical properties and insecticidal potential

Herein described is the biochemical characterisation, including in vitro and in vivo assays, for a proteinase inhibitor purified from Clitoria fairchildiana seeds (CFPI). Purification was performed by hydrophobic interaction and gel filtration chromatography. Kinetic studies of the purified inhibitor showed a competitive-type inhibitory activity against bovine trypsin and chymotrypsin, with an inhibition stoichiometry of 1:1 for both enzymes. The inhibition constants against trypsin and chymotrypsin were 3.3 × 10(-10) and 1.5 × 10(-10)M, respectively, displaying a tight binding property. SDS-PAGE showed that CFPI has a single polypeptide chain with an apparent molecular mass of 15 kDa under non-reducing conditions. However, MALDI-TOF analysis demonstrated a molecular mass of 7.973 kDa, suggesting that CFPI is dimeric in solution. The N-terminal sequence of CFPI showed homology with members of the Bowman-Birk inhibitor family. CFPI remained stable to progressive heating for 30 min to each temperature range of 37 up to 100 °C and CD analysis exhibited no changes in spectra at 207 nm after heating at 90 °C and subsequent cooling. Moreover, CFPI was active over a wide pH range (2-10). In contrast, reduction with DTT resulted in a loss of inhibitory activity against trypsin and chymotrypsin. CFPI also exhibited significant inhibitory activity against larval midgut trypsin enzymes from Anagasta kuehniella (76%), Diatraea saccharalis (59%) and Heliothis virescens (49%). Its insecticidal properties were further analysed by bioassays and confirmed by negative impact on A. kuehniella development.

Entomotoxic properties of Dioclea violacea lectin and its effects on digestive enzymes of Anagasta kuehniella (Lepidoptera)

Entomotoxic plant lectins have been extensively studied in the past two decades, yet the exact mechanisms underlying their toxic effects remain unknown. This study investigated the effects of Dioclea violacea lectin (DVL) on larval development in Anagasta kuehniella. Chronic exposure of larvae (from neonates to the fourth instar) demonstrated that DVL interfered with larval growth, retarding development and decreasing larval mass without affecting survival. DVL decreased trypsin-like, chymotrypsin-like, and α-amylase activities and proved resistant to proteolysis by midgut proteases up to 24h. Shorter exposures to dietary DVL had no effect on midgut enzyme activity. Feeding fourth-instar larvae with fluorescently-labeled DVL revealed lectin binding to the peritrophic membrane.

Purification and characterization of a Kunitz inhibitor from Poincianella pyramidalis with insecticide activity against the Mediterranean flour moth

This paper describes the characterization of a trypsin inhibitor from Poincianella pyramidalis seeds (PpyTI). The partial sequencing of PpyTI revealed homology to Kunitz inhibitors, clustered as a member of Family I03 in MEROPS database. PpyTI has a single polypeptide chain of 19,042 Da and presents stability at high temperatures (up to 70 °C) and a wide range of pH. In vitro assays showed that disulfide bridges have an important stabilization role of reactive site in PpyTI, a characteristic shared among several Kunitz inhibitors. Bioassays carried out with the Mediterranean flour moth (Anagasta kuehniella) revealed a significant decrease in both larval weight and survival of PpyTI-fed larvae, besides a larval stage extension. Through biochemical analysis, we demonstrated that the PpyTI insecticide effects were triggered by digestion process commitment, through the inhibition of trypsin and chymotrypsin activities, the major digestive enzymes in this species. The insecticide effects and biochemical characterization of PpyTI encourage further studies using this inhibitor for insect pest control.

The trypsin inhibitor from Entada acaciifolia seeds affects negatively the development of Mediterranean flour moth, Anagasta kuehniella

The Mediterranean flour moth (Anagasta kuehniella) is a pest insect that attacks stored foods. The difficulty in controlling this kind of pest promotes the development of alternatives for pest control, among them the use of proteins with insecticide effect. In this work, we evaluated the role of a trypsin inhibitor purified from Entada acaciifolia seeds (EATI) on the A. kuehniella development. Different concentrations of inhibitor were added to a diet to determine its effects on insect performance. At 0.4%, the EATI decreases the larval weight and survival rates by 54.6% and 15%, respectively; in addition to the extension of the life cycle of insect. The biochemical analysis showed that the inhibitor is refractory to the digestion by midgut proteases, and led to a reduction of 32% in general proteolytic activity. A detailed analysis of the enzymatic activity revealed a decrease of 50% in trypsin activity as the chymotrypsin activity increased by 12%; possibly to compensate the commitment of the digestive process. The trypsins from the EATI-fed group stayed sensitive to the inhibition by EATI, and based on kinetic assays no new trypsin enzymes were produced as adaptation attempt. The insecticides effects observed for the EATI against this pest encourage a more in depth study of its possible long-term use as a biotechnological tool.