Insight into the biochemical, kinetic and spectroscopic characterization of garlic (Allium sativum) phytocystatin: Implication for cardiovascular disease

Characterization and kinetics of a cathepsin B-inhibiting protein from Musa acuminata Colla peel

Hyperexpression of cathepsin B caused by an imbalance of endogenous inhibitors is involved in multiple pathologies, hence making it a key therapeutic target. Protease inhibitors are effective biomolecules that regulate protease activities and are considered potential therapeutic agents in various diseases. Plant protease inhibitors have been reported as an effective complementary alternative drug. A proteinaceous cathepsin B inhibitor (CBI-BP) has been isolated from Musa acuminata Colla (banana) peel with a molecular weight of 27.9 kDa on SDS-PAGE. The purity of the CBI-BP was confirmed on the native- PAGE. The isolated CBI-BP showed an IC50 value of 8.14 μg and a Ki value of 10.59 μg (0.19 μM). Cathepsin B inhibition kinetics indicated that CBI-BP follows a mixed-type of cathepsin B inhibition. Its inhibition activity was also confirmed by reverse zymography. The inhibitor was stable from pH 2.6-10.0 with maximum activity at pH 7.2, temperature 25-100 °C and exhibited thermostability for 60 min at 70 °C. MALDI/TOF/MS analysis of CBI-BP showed 40 % similarity to the GH18 domain-containing protein (A0A4S8JRM9) from Musa balbisiana. Although in-silico docking studies showed binding of A0A4S8JRM9 to cathepsin B affects the binding energy of the substrate to cathepsin B but is not reported for any anti-cathepsin B activity. This suggests that isolated CBI-BP might be a novel protein with anti-cathepsin B activity. Thus the isolated CBI-BP may be further explored as possible anti-cathepsin B drug.

Assessment of standardization of domestic commercial black garlic extract for S-allyl-l-cysteine and S-1-propenyl-l-cysteine

Aged garlic extract (AGE) contains a significant amount of bioactive compounds, including S-allyl-l-cysteine (SAC), which is associated with various health benefits. Among different AGE products, black garlic extract (BGE) is widely consumed and a common product in the Korean market. BGE products do however contain different levels of SAC and S1PC. Here, the SAC contents in commercial BGE products were found to be in the range of 0.31-27.22 mg/100 mL, while the SAC contents of commercial black garlic (BG) cloves were in the range of 22.28-63.71 mg/100 g. Recently, S-1-propenyl-l-cysteine (S1PC) has emerged as a new bioactive compound of interest in AGE products. Analysis of BG and BGE indicated that their S1PC contents were 2.24-16.58 mg/100 g and ND-3.68 mg/100 mL, respectively. Based on the significance of these compounds, standardization of the SAC and S1PC content in commercial BGE products is required.

Purification and Characterization of a Novel Thermostable Papain Inhibitor from Moringa oleifera with Antimicrobial and Anticoagulant Properties

Plant cystatins (or phytocystatins) comprise a large superfamily of natural bioactive small proteins that typically act as protein inhibitors of papain-like cysteine proteases. In this report, we present the purification and characterization of the first phytocystatin isolated from Moringa oleifera (MoPI). MoPI has a molecular mass of 19 kDa and showed an extraordinary physicochemical stability against acidic pHs and high temperatures. Our findings also revealed that MoPI is one of the most potent cysteine protease inhibitors reported to date, with Ki and IC₅₀ values of 2.1 nM and 5.7 nM, respectively. More interestingly, MoPI presents a strong antimicrobial activity against human pathogens such as Enterococcus faecalis and Staphylococcus aureus. In addition, MoPI also showed important anticoagulant activity, which is an unprecedented property for this family of protease inhibitors. These results highlight the pharmaceutical potential of this plant and its derived bioactive molecules.

Biotechnological Potential of Araucaria angustifolia Pine Nuts Extract and the Cysteine Protease Inhibitor AaCI-2S

Protease inhibitors are involved in the regulation of endogenous cysteine proteases during seed development and play a defensive role because of their ability to inhibit exogenous proteases such as those present in the digestive tracts of insects. Araucaria angustifolia seeds, which can be used in human and animal feed, were investigated for their potential for the development of agricultural biotechnology and in the field of human health. In the pine nuts extract, which blocked the activities of cysteine proteases, it was detected potent insecticidal activity against termites (Nasutitermes corniger) belonging to the most abundant termite genus in tropical regions. The cysteine inhibitor (AaCI-2S) was purified by ion-exchange, size exclusion, and reversed-phase chromatography. Its functional and structural stability was confirmed by spectroscopic and circular dichroism studies, and by detection of inhibitory activity at different temperatures and pH values. Besides having activity on cysteine proteases from C. maculatus digestive tract, AaCI-2S inhibited papain, bromelain, ficin, and cathepsin L and impaired cell proliferation in gastric and prostate cancer cell lines. These properties qualify A. angustifolia seeds as a protein source with value properties of natural insecticide and to contain a protease inhibitor with the potential to be a bioactive molecule on different cancer cells.

Biotechnological, biomedical, and agronomical applications of plant protease inhibitors with high stability: A systematic review

Protease inhibitors (PIs) are regulatory proteins found in numerous animal tissues and fluids, plants, and microorganisms that reduce and inhibit the exacerbated and uncontrolled activity of the target proteases. Specific PIs are also effective tools for inactivating proteases involved in human diseases like arthritis, pancreatitis, hepatitis, cancer, AIDS, thrombosis, emphysema, hypertension, and muscular dystrophy among others. Plant PIs-small peptides with a high content of cystine residues in disulfide bridges-possess a remarkable resistance to heat treatment and a high stability against shifts in pH, denaturing agents, ionic strength, and proteolysis. In recent years, novel biologic activities have been reported for plant PIs, including antimicrobial, anticoagulant, antioxidant action plus inhibition of tumor-cell growth; thus pointing to possible applications in medicine, agriculture, and biotechnology. In this review, we provide a comparative overview of plant-PIs classifying them in four groups according of their thermal and pH stability (high stability and hyperstable -to temperature and to pHs-, respectively), then emphasizing the relevance of the physicochemical characteristics of these proteins for potential biotechnological and industrial applications. Finally, we analyze the biologic activities of the stable protease inhibitors previously characterized that are the most relevant to potential applications in biomedicine, the food industry, and agriculture.

Insight into the biochemical characterization of phytocystatin from Glycine max and its interaction with Cd+2 and Ni+2

Phytocystatins are cysteine proteinase inhibitors ubiquitously present in plants and animals. They are known to carry out various significant physiological functions and also maintain the balance of protease-antiprotease activity. In the present disquisition, a phytocystatin after preliminary treatment has been isolated and purified to homogeneity from soybean (Glycine max) by a simple two-step stratagem using ammonium sulfate fractionation and gel filtration chromatography performed on Sephacryl S-100-HR. Soybean phytocystatin (SBPC) was purified with a fold purification of 635 and percent yield of 77.6%. A single band was observed on native gel electrophoresis confirming the homogeneity of the purified SBPC. The molecular weight of SBPC was found to be 19.05 kDa as determined by SDS-PAGE. The SBPC was found to be devoid of carbohydrate moieties and sulfhydryl group content. The binding stoichiometry of SBPC-papain interaction was determined by isothermal calorimetry suggesting 1:1 complex, and the value of binding constant (K) was found to be 2.78 × 105  M-1 The affinity of binding (Kd ) value obtained through ITC was 3.59 × 10-6  M. The purified SBPC was found to be stable in the pH range of 3 to 7 and is thermostable up to 50°C. The UV-visible and fluorescence studies showed significant changes in the conformation upon the formation of the SBPC-papain complex. Furthermore, fluorescence spectroscopy, ANS binding, and caseinolytic activity assay were conducted out to explore the effect of metal ions on SBPC which showed that there was a loss in the inhibitory activity along with conformational changes of SBPC upon complex formation with Cd+2 and Ni+2 .

ClCPI, a cysteine protease inhibitor purified from Cassia leiandra seeds has antifungal activity against Candida tropicalis by inducing disruption of the cell surface

Infections caused by Candida tropicalis have increased significantly worldwide in parallel with resistance to antifungal drugs. To overcome resistance novel drugs have to be discovered. The objective of this work was to purify and characterize a cysteine protease inhibitor from the seeds of the Amazon rainforest tree Cassia leiandra and test its inhibitory effect against C. tropicalis growth. The inhibitor, named ClCPI, was purified after ion exchange and affinity chromatography followed by ultrafiltration. ClCPI is composed of a single polypeptide chain and is not a glycoprotein. The molecular mass determined by SDS-PAGE in the absence or presence of β-mercaptoethanol and ESI-MS were 16.63 kDa and 18.362 kDa, respectively. ClCPI was stable in the pH range of 7.0-9.0 and thermostable up to 60 °C for 20 min. ClCPI inhibited cysteine proteases, but not trypsin, chymotrypsin neither alpha-amylase. Inhibition of papain was uncompetitive with a Ki of 4.1 × 10^-7 M and IC₅₀ of 8.5 × 10^-7 M. ClCPI at 2.6 × 10^-6 M reduced 50% C. tropicalis growth. ClCPI induced damages and morphological alterations in C. tropicalis cell surface, which led to death. These results suggest that ClCPI have great potential for the development of an antifungal drug against C. tropicalis.

A biophysical insight into the formation of aggregates upon trifluoroethanol induced structural and conformational changes in garlic cystatin

Intrinsic and extrinsic factors are responsible for the transition of soluble proteins into aggregated form. Trifluoroethanol is among such potent extrinsic factor which facilitates the formation of aggregated structure. It disrupts the interactive forces and destabilizes the native structure of the protein. The present study investigates the effect of trifluoroethanol (TFE) on garlic cystatin. Garlic cystatin was incubated with increasing concentration of TFE (0-90% v/v) for 4 h. Incubation of GPC with TFE induces structural changes thereby resulting in the formation of aggregates. Inactivation of garlic phytocystatin was confirmed by cysteine proteinase inhibitory activity. Garlic cystatin at 30% TFE exhibits native-like secondary structure and high ANS fluorescence, thus suggesting the presence of molten globule state. Circular dichroism and FTIR confirmed the transition of the native alpha-helical structure of garlic cystatin to the beta-sheet structure at 60% TFE. Furthermore, increased ThT fluorescence and redshift in Congo red absorbance assay confirmed the presence of aggregates. Rayleigh and turbidity assay was also performed to validate the aggregation results. Scanning electron microscopy was followed to analyze the morphological changes which confirm the presence of sheath-like structure at 60% TFE. The study sheds light on the conformational behavior of a plant protein when kept under stress condition induced by an extrinsic factor.

Black Garlic Improves Heart Function in Patients With Coronary Heart Disease by Improving Circulating Antioxidant Levels

Background: Black garlic (BG) has many health-promoting properties.

Objectives: We aimed to explore the clinical effects of BG on chronic heart failure (CHF) in patients with coronary heart disease (CHD).

Design: The main components of BG were measured by gas chromatography–mass spectrometry (GC–MS) and its antioxidant properties were determined by the clearance rate of free radicals. One hundred twenty CHF patients caused by CHD were randomly and evenly assigned into BG group and placebo group (CG). The duration of treatment was 6 months. Cardiac function was measured according to the New York Heart Association (NYHA) functional classification system. The following parameters were measured, including walking distance, BNP precursor N-terminal (Nt-proBNP), left-ventricular ejection fraction (LVEF) value, and the scores of quality of life (QOL). The circulating antioxidant levels were compared between two groups.

Results: There are 27 main compounds in BG with strong antioxidant properties. BG treatment improved cardiac function when compared with controls (P < 0.05). The QOL scores and LVEF values were higher in the BG group than in the CG group while the concentration of Nt-proBNP was lower in the BG group than in the CG group (P < 0.05). Circulating antioxidant levels were higher in the BG group than in the CG group. Antioxidant levels had positive relation with QOL and LVEF values, and negative relation with Nt-proBNP values.

Conclusion: BG improves the QOL, Nt-proBNP, and LVEF in CHF patient with CHD by increasing antioxidant levels.

Exposure of carbendazim induces structural and functional alteration in garlic phytocystatin: An in vitro multi-spectroscopic approach

Carbendazim is a broad spectrum benzimidazole fungicide which is used to ensure plants' protection from pest and pathogens' invasion. The present work describes the impact of carbendazim (CAR) on garlic phytocystatin (GPC) which is a crucial plant regulatory protein. Interaction of carbendazim with GPC has been investigated through various biophysical techniques viz. UV absorption, fluorescence spectroscopy, isothermal titration calorimetry, far-UV circular dichroism and FTIR spectroscopy which showed binding between them with consequent modulatory effects. Functional activity of GPC was monitored by the anti-papain inhibitory assay which suggests that incubation of GPC with the higher concentration of CAR disrupts the inhibitory function of GPC. UV spectroscopy confirmed the formation of GPC-CAR complex. Intrinsic fluorescence suggests binding of CAR to GPC which reflects the changes in microenvironment around tryptophan residues of GPC. Isothermal titration calorimetry suggests that interaction of CAR to GPC is an exothermic reaction. Secondary structure analysis was also performed which confirmed that binding of CAR decreases the alpha-helical content of GPC. Collectively, these results demonstrated that GPC exhibited significant structural and functional alteration upon interaction with carbendazim. Since GPC is involved in various regulatory processes, therefore, its structural or functional alteration may lead to disruption of physiological and biological balance within the plant. Hence, our study signifies that exposure of carbendazim to plant exerts physicochemical alteration within the plant.