New insights into the complex mixture of latex cysteine peptidases in Calotropis procera

Crystal Structure of Papain-Like Cysteine Protease, Calotropain FI, Purified from the Latex of Calotropis gigantea

The latex of Calotropis gigantea and Calotropis procera elute as two distinct peaks on cation exchange chromatography. One of the peaks is reported to possess multiple papain-like cysteine proteases with different biochemical properties that have been identified with different names. This is mainly due to the absence of a primary sequence for the proteases. Here, we report the crystal structures of calotropain FI from C. gigantea bound to the inhibitor E64 at pH 6 and 9 at 1.25 and 1.4 Å, respectively. Both structures are identical and are very similar to ervatamin B and papain structures. The high quality of electron density maps revealed the primary sequence of calotropain FI. The sequence comparison shows that calotropain FI from C. gigantea is orthologous to procerain, CpCp1-3, and SnuCalCp03 from C. procera and rather distinct from procerain B.

Recent discovery of natural substances with cathepsin L-inhibitory activity for cancer metastasis suppression

Cathepsin L (CTSL), a cysteine cathepsin protease of the papain superfamily, plays a crucial role in cancer progression and metastasis. Dysregulation of CTSL is frequently observed in tumor malignancies, leading to the degradation of extracellular matrix and facilitating epithelial-mesenchymal transition (EMT), a key process in malignant cancer metastasis. This review mainly provides a comprehensive information about recent findings on natural inhibitors targeting CTSL and their anticancer effects, which have emerged as potent anticancer therapeutic agents or metastasis-suppressive adjuvants. Specifically, inhibitors are categorized into small-molecule and macromolecule inhibitors, with a particular emphasis on cathepsin propeptide-type macromolecules. Additionally, the article explores the molecular mechanisms of CTSL involvement in cancer metastasis, highlighting its regulation at transcriptional, translational, post-translational, and epigenetic levels. This work underscores the importance of understanding natural CTSL inhibitors and provides researchers with practical insights to advance the relevant fields and discover novel CTSL-targeting inhibitors from natural sources.

Recombinant protein production for structural and kinetic studies: A case study using M. tuberculosis α-methylacyl-CoA racemase (MCR)

Modern drug discovery is a target-driven approach in which a particular protein such as an enzyme is implicated in the disease process. Commonly, small-molecule drugs are identified using screening, rational design, and structural biology approaches. Drug screening, testing and optimization is typically conducted in vitro, and copious amounts of protein are required. The advent of recombinant DNA technologies has resulted in a rise in proteins purified by affinity techniques, typically by incorporating an "affinity tag" at the N- or C-terminus. Use of these tagged proteins and affinity techniques comes with a host of issues. This chapter describes the production of an untagged enzyme, α-methylacyl-CoA racemase (MCR) from Mycobacterium tuberculosis, using a recombinant E. coli system. Purification of the enzyme on a 100 mg scale using tandem anion-exchange chromatographies (DEAE-sepharose and RESOURCE-Q columns), and size-exclusion chromatographies is described. A modified protocol allowing the purification of cationic proteins is also described, based on tandem cation-exchange chromatographies (using CM-sepharose and RESOURCE-S columns) and size-exclusion chromatographies. The resulting MCR protein is suitable for biochemical and structural biology applications. The described protocols have wide applicability to the purification of other recombinant proteins and enzymes without using affinity chromatography.

Phytomodulatory proteins isolated from Calotropis procera latex promote glycemic control by improving hepatic mitochondrial function in HepG2 cells

The medicinal uses of Calotropis procera are diverse, yet some of them are based on effects that still lack scientific support. Control of diabetes is one of them. Recently, latex proteins from C. procera latex (LP) have been shown to promote in vivo glycemic control by the inhibition of hepatic glucose production via AMP-activated protein kinase (AMPK). Glycemic control has been attributed to an isolated fraction of LP (CpPII), which is composed of cysteine peptidases (95%) and osmotin (5%) isoforms. Those proteins are extensively characterized in terms of chemistry, biochemistry and structural aspects. Furthermore, we evaluated some aspects of the mitochondrial function and cellular mechanisms involved in CpPII activity. The effect of CpPII on glycemic control was evaluated in fasting mice by glycemic curve and glucose and pyruvate tolerance tests. HepG2 cells was treated with CpPII, and cell viability, oxygen consumption, PPAR activity, production of lactate and reactive oxygen species, mitochondrial density and protein and gene expression were analyzed. CpPII reduced fasting glycemia, improved glucose tolerance and inhibited hepatic glucose production in control animals. Additionally, CpPII increased the consumption of ATP-linked oxygen and mitochondrial uncoupling, reduced lactate concentration, increased protein expression of mitochondrial complexes I, III and V, and activity of peroxisome-proliferator-responsive elements (PPRE), reduced the presence of reactive oxygen species (ROS) and increased mitochondrial density in HepG2 cells by activation of AMPK/PPAR. Our findings strongly support the medicinal use of the plant and suggest that CpPII is a potential therapy for prevention and/or treatment of type-2 diabetes. A common epitope sequence shared among the proteases and osmotin is possibly the responsible for the beneficial effects of CpPII.

Cohnella 1759 cysteine protease shows significant long term half-life and impressive increased activity in presence of some chemical reagents

Thermostability and substrate specificity of proteases are major factors in their industrial applications. rEla is a novel recombinant cysteine protease obtained from a thermophilic bacterium, Cohnella sp.A01 (PTCC No: 1921). Herein, we were interested in recombinant production and characterization of the enzyme and finding the novel features in comparison with other well-studied cysteine proteases. The bioinformatics analysis showed that rEla is allosteric cysteine protease from DJ-1/ThiJ/PfpI superfamily. The enzyme was heterologously expressed and characterized and the recombinant enzyme molecular mass was 19.38 kD which seems to be smaller than most of the cysteine proteases. rEla exhibited acceptable activity in broad pH and temperature ranges. The optimum activity was observed at 50℃ and pH 8 and the enzyme showed remarkable stability by keeping 50% of residual activity after 100 days storage at room temperature. The enzyme Km and Vmax values were 21.93 mM, 8 U/ml, respectively. To the best of our knowledge, in comparison with the other characterized cysteine proteases, rEla is the only reported cysteine protease with collagen specificity. The enzymes activity increases up to 1.4 times in the presence of calcium ion (2 mM) suggesting it as the enzyme's co-factor. When exposed to surfactants including Tween20, Tween80, Triton X-100 and SDS (1% and 4% v/v) the enzyme activity surprisingly increased up to 5 times.

Perspectives for the use of latex peptidases from Calotropis procera for control of inflammation derived from Salmonella infections

BACKGROUND

Anti-inflammatory properties have been attributed to latex proteins of the medicinal plant Calotropis procera.

PURPOSE

A mixture of cysteine peptidases (LPp2) from C. procera latex was investigated for control of inflammatory mediators and inflammation in a mouse model of Salmonella infection.

METHODS

LPp2 peptidase activity was confirmed by the BANA assay. Cytotoxicity assays were conducted with immortalized macrophages. Peritoneal macrophages (pMØ) from Swiss mice were stimulated with lipopolysaccharide (LPS) in 96-well plates and then cultured with nontoxic concentrations of LPp2. Swiss mice intravenously received LPp2 (10 mg/kg) and then were challenged intraperitoneally with virulent Salmonella enterica Ser. Typhimurium.

RESULTS

LPp2 was not toxic at dosages lower than 62.2 μg/mL. LPp2 treatments of pMØ stimulated with LPS impaired mRNA expression of pro-inflammatory cytokines IL-1β, TNF-α, IL-6 and IL-10. LPp2 increased the intracellular bacterial killing in infected pMØ. Mice given LPp2 had a lower number of leukocytes in the peritoneal cavity in comparison to control groups 6 h after infection. The bacterial burden and histological damage were widespread in target organs of mice receiving LPp2.

CONCLUSION

We conclude that LPp2 contains peptidases with strong anti-inflammatory properties, which may render mice more susceptible to early disseminated infection caused by Salmonella.

An Overview of the Characteristics and Potential of Calotropis procera From Botanical, Ecological, and Economic Perspectives

Calotropis procera (Aiton) Dryand. (commonly known as the apple of sodom, calotrope, and giant milkweed) is an evergreen, perennial shrub of the family Apocynaceae, mainly found in arid and semi-arid regions. It is a multipurpose plant, which can be utilized for medicine, fodder, and fuel purposes, timber and fiber production, phytoremediation, and synthesis of nanoparticles. It has been widely used in traditional medicinal systems across North Africa, Middle East Asia, and South-East Asia. At present, it is being extensively explored for its potential pharmacological applications. Several reports also suggest its prospects in the food, textile, and paper industries. Besides, C. procera has also been acknowledged as an ornamental species. High pharmacological potential and socio-economic value have led to the pantropical introduction of the plant. Morpho-physiological adaptations and the ability to tolerate various abiotic stresses enabled its naturalization beyond the introduced areas. Now, it is recognized as an obnoxious environmental weed in several parts of the world. Its unnatural expansion has been witnessed in the regions of South America, the Caribbean Islands, Australia, the Hawaiian Islands, Mexico, Seychelles, and several Pacific Islands. In Australia, nearly 3.7 million hectares of drier areas, including rangelands and Savannahs, have been invaded by the plant. In this review, multiple aspects of C. procera have been discussed including its general characteristics, current and potential uses, and invasive tendencies. The objectives of this review are a) to compile the information available in the literature on C. procera, to make it accessible for future research, b) to enlist together its potential applications being investigated in different fields, and c) to acknowledge C. procera as an emerging invasive species of arid and semi-arid regions.

In vitro haemostatic efficacy of aqueous, methanol and ethanol plant extracts of three medicinal plant species in Palestine

Abstract The haemostatic efficacy of different extract types of Satureja thymbra L., Thymbra spicata L. (Lamiaceae) and Verbascum fruticulosum Post. (Scrophulariaceae) was evaluated in this study via the Prothrombin time (PT) and Activated partial thromboplastin time (aPTT) analysis. Aqueous, methanol and ethanol extracts of the examined plant species leaves were prepared to a final concentration 50 mg/mL. In vitro PT and aPTT assays were conducted on normal platelet poor plasma blood samples by a digital coagulation analyzer. The obtained results revealed anticoagulation activity of all investigated plant species with observed variations among them. The aqueous and ethanol extracts of T. spicata as well as the aqueous extract of S. thymbra prolonged PT values significantly (p < 0.05). While, all V. fruticulosum extract types have had no significant effect on the PT values. The recorded aPTT data showed that all aqueous extracts have had a significant effect on the blood haemostasis as they increased aPTT values in all plant species under study. Out of which, both the ethanol and methanol extracts of T. spicata and methanol extract of S. thymbra showed similar effect. Of great concern, it was clearly noticed that the aqueous and ethanol extract of T. spicata and the aqueous extract of S. thymbra possess the strongest anticoagulation effect as they increased both PT and aPTT values significantly relative to the control (p < 0.05). The variable anticoagulation bioactivity among the studied plant species could be referred to the various solvents degrees of solubility of different phyto-constituents. Thus, the efficacy of the plant species extracts evaluation as anticoagulants or coagulants were related to the plant species and to the solvent of extraction.

Latex proteins downregulate inflammation and restores blood-coagulation homeostasis in acute Salmonella infection

BACKGROUND

Calotropis procera latex protein fraction (LP) was previously shown to protect animals from septic shock. Further investigations showed that LP modulate nitric oxide and cytokines levels.

OBJECTIVES

To evaluate whether the protective effects of LP, against lethal bacterial infection, is observed in its subfractions (LP_PII and LP_PIII).

METHODS

Subfractions (5 and 10 mg/kg) were tested by i.p. administration, 24 h before challenging with lethal injection (i.p.) of Salmonella Typhimurium. LP_PIII (5 mg/kg) which showed higher survival rate was assayed to evaluate bacterial clearance, histopathology, leukocyte recruitment, plasma coagulation time, cytokines and NO levels.

FINDINGS

LP_PIII protected 70% of animals of death. The animals given LP_PIII exhibited reduced bacterial load in blood and peritoneal fluid after 24 h compared to the control. LP_PIII promoted macrophage infiltration in spleen and liver. LP_PIII restored the coagulation time of infected animals, increased IL-10 and reduced NO in blood.

MAIN CONCLUSIONS

LP_PIII recruited macrophages to the target organs of bacterial infection. This addressed inflammatory stimulus seems to reduce bacterial colonisation in spleen and liver, down regulate bacterial spread and contribute to avoid septic shock.

Crystal structure and specific location of a germin-like protein with proteolytic activity from Thevetia peruviana

Peruvianin-I is a cysteine peptidase (EC 3.4.22) purified from Thevetia peruviana. Previous studies have shown that it is the only germin-like protein (GLP) with proteolytic activity described so far. In this work, the X-ray crystal structure of peruvianin-I was determined to a resolution of 2.15 Å (PDB accession number: 6ORM) and its specific location was evaluated by different assays. Its overall structure shows an arrangement composed of a homohexamer (a trimer of dimers) where each monomer exhibits a typical β-barrel fold and two glycosylation sites (Asn₅₅ and Asn₁₄₄). Analysis of its active site confirmed the absence of essential amino acids for typical oxalate oxidase activity of GLPs. Details of the active site and molecular docking results, using a specific cysteine peptidase inhibitor (iodoacetamide), were used to discuss a plausible mechanism for proteolytic activity of peruvianin-I. Histological analyses showed that T. peruviana has articulated anastomosing laticifers, i.e., rows of cells which merge to form continuous tubes throughout its green organs. Moreover, peruvianin-I was detected exclusively in the latex. Because latex peptidases have been described as defensive molecules against insects, we hypothesize that peruvianin-I contributes to protect T. peruviana plants against herbivory.

Anti-inflammatory latex proteins of the medicinal plant Calotropis procera: a promising alternative for oral mucositis treatment

OBJECTIVE AND DESIGN

Oral mucositis (OM) is an intense inflammatory reaction progressing to tissue damage and ulceration. The medicinal uses of Calotropis procera are supported by anti-inflammatory capacity. PII-IAA, a highly homogenous cocktail of laticifer proteins (LP) prepared from the latex of C. procera, with recognized pharmacological properties was tested to treat OM.

MATERIALS AND SUBJECTS

Male Golden Sirius hamsters were used in all treatments.

TREATMENT

The latex protein samples were injected i.p. (5 mg/Kg) 24 h before mucositis induction (mechanical trauma) and 24 h later.

METHODS

Histology, cytokine measurements [ELISA], and macroscopic evaluation [scores] were performed.

RESULTS

PII-IAA eliminated OM, accompanied by total disappearance of myeloperoxidase activity and release of IL-1b, as well as reduced TNF-a. Oxidative stress was relieved by PII-IAA treatment, as revealed by MDA and GSH measurements. PII-IAA also reduced the expression of adhesion molecules (ICAM-1) and Iba-1, two important markers of inflammation, indicating modulatory effects. Histological analyses of the cheek epithelium revealed greater deposition of type I collagen fibers in animals given PII-IAA compared with the control group. This performance was only reached when LPPII was treated with iodoacetamide (IAA), an irreversible inhibitor of proteolytic activity of cysteine proteases. The endogenous proteolytic activity of LPPII induced adverse effects in animals. Candidate proteins involved in the phytomodulatory activity are proposed.

CONCLUSIONS

Therapy was successful in treating OM with the laticifer protein fraction, containing peptidases and osmotin, from Calotropis procera. The effective candidate from the latex proteins for therapeutic use is PII-IAA.

Biotechnological potential of a cysteine protease (CpCP3) from Calotropis procera latex for cheesemaking

This article reports the characterization and evaluation of the biotechnological potential of a cysteine protease purified from Calotropis procera (CpCP3). This enzyme was highly stable to different metal ions and was able to hydrolyze κ-casein similarly to bovine chymosin. Atomic force microscopy showed that the process of casein micelle aggregation induced by CpCP3 was similar to that caused by chymosin. The cheeses made using CpCP3 showed higher moisture content than those made with chymosin, but protein, fat, and ash were similar. The sensory analysis showed that cheeses made with CpCP3 had high acceptance index (>80%). In silico analysis predicted the presence of only two short allergenic peptides on the surface of CpCP3, which was highly susceptible to digestive enzymes and did not alter zebrafish embryos' morphology and development. Moreover, recombinant CpCP3 was expressed in Escherichia coli. All results support the biotechnological potential of CpCP3 as an alternative enzyme to chymosin.

Chemical constituents of Calotropis procera latex and ultrastructural effects on Haemonchus contortus

Abstract This study aimed to evaluate the anthelmintic and ultrastructural effects of Calotropis procera latex on Haemonchus contortus. C. procera latex was twice centrifuged at 10,000×g and dialyzed to obtain a fraction rich in proteins, named LP (latex protein), and at 3,000 rpm to obtain a fraction rich in secondary metabolites, named LNP (latex non-protein). Specimens of H. contortus exposed to LNP, LP and PBS in the Adult Worm Motility Test (AWMT) were submitted to scanning (SEM) and transmission (TEM) electron microscopy to verify changes in their ultrastructure. Phytochemical tests in the LNP indicated the presence of phenols, steroids, alkaloids and cardenolides. High-Performance Liquid Chromatography (HPLC) characterized the presence of the compounds gallic acid and quercetin in the LNP. The protein content in the LP was 43.1 ± 1.1 mg/mL and 7.7 ± 0.3 mg/mL in LNP. In AWMT, LNP and LP inhibited the motility of 100% of the nematodes, with LNP being more effective than LP and ivermectin more effective than both (p <0.05). Cuticle changes were observed by SEM and TEM in nematodes treated with LP and LNP. Calotropis procera latex has anthelmintic effects against H. contortus, causing damage to its cuticle and other alterations in its ultrastructure.

Identification, characterization, and antifungal activity of cysteine peptidases from Calotropis procera latex

Cysteine peptidases (EC 3.4.22) are the most abundant enzymes in latex fluids. However, their physiological functions are still poorly understood, mainly related to defense against phytopathogens. The present study reports the cDNA cloning and sequencing of five undescribed cysteine peptidases from Calotropis procera (Aiton) Dryand (Apocynaceae) as well as some in silico analyses. Of these, three cysteine peptidases (CpCP1, CpCP2, and CpCP3) were purified. Their enzymatic kinetics were determined and they were assayed for their efficacy in inhibiting the hyphal growth of phytopathogenic fungi. The mechanism of action was investigated by fluorescence and atomic force microscopy as well as by induction of reactive oxygen species (ROS). The deduced amino acid sequences showed similar biochemical characteristics and high sequence homology with several other papain-like cysteine peptidases. Three-dimensional models showed two typical cysteine peptidase domains (L and R domains), forming a "V-shaped" active site containing the catalytic triad (Cys, His, and Asn). Proteolysis of CpCP1 was higher at pH 7.0, whereas for CpCP2 and CpCP3 it was higher at 7.5. All peptidases exhibited optimum activity at 35 °C and followed Michaelis-Menten kinetics. However, the major difference among them was that CpCP1 exhibited highest V_max, K_m, K_cat and catalytic efficiency. All peptidases were deleterious to the two fungi tested, with IC₅₀ of around 50 μg/mL. The peptidases promoted membrane permeabilization, morphological changes with leakage of cellular content, and induction of ROS in F. oxysporum spores. These results corroborate the hypothesis that latex cysteine peptidases play a role in defense against fungi.

Inhibition of apricot polyphenol oxidase by combinations of plant proteases and ascorbic acid

The present research investigates the long term inhibition of enzymatic browning by inactivating the polyphenol oxidase (PPO) of apricot, using combinations of plant proteases and ascorbic acid (AA). The selected proteases were able to inactivate PPO at pH 4.5, with the degree of inactivation proportional to incubation time and protease concentration. Papain was the most effective protease, with 50 μg completely inactivating PPO in less than one hour. AA prevented browning reactions that occur before or during PPO inactivation by protease. The combinations of AA/proteases were highly effective in vitro, where 2 mM AA/500 μg proteases inhibited PPO activity completely over 24 h. The combination of AA/proteases was also effective in vivo, as treated apricot purees preserved their color (p < 0.0001, compared to untreated samples after 10 days of storage). The results demonstrate that AA/proteases combinations constitute a promising practical anti-browning method with feasible application in the food industry.

Erythrocytes morphology and hemorheology in severe bacterial infection

BACKGROUND

Severe bacterial infections initiate inadequate inflammation that leads to disseminated intravascular coagulation and death.

OBJECTIVES

To evaluate the influence of bacterial infection on blood viscosity and red blood cells (RBCs) morphology, and the ability of Calotropis procera proteins (CpLP) to prevent the patho-hemorheology in infected animals.

METHODS

Rheology of blood, atomic force microscopy measurements on specific blood elements and blood count were performed to examine changes in blood viscosity, RBCs morphology, platelets activation, and RBCs indices.

FINDINGS

Infected mice hold their blood rheological behaviour as compared to that of the control group. However, they presented hyperactivated platelets, RBCs at different stages of eryptosis, and variation on RBCs indices. CpLP administration in healthy animals altered blood behaviour from pseudoplastic to Bingham-like fluid. Such effect disappeared over time and by inhibiting its proteases. No alterations were observed in RBCs morphology or platelets. Treatment of infected animals with CpLP prevented the changes in RBCs indices and morphology.

MAIN CONCLUSIONS

The inflammatory process triggered by bacterial infection induced pathological changes in RBCs and platelets activation. Treatment of infected animals with CpLP prevented the emergence of RBCs abnormal morphology and this may have implications in the protective effect of CpLP, avoiding animal death.

Laticifers, Latex, and Their Role in Plant Defense

Latex, a sap produced by cells called laticifers, occurs in plants of wide taxonomic diversity. Plants exude latex sap in response to physical damage. Questions about the function of latex or the underlying mechanisms persist, but a role in defense is likely. The presence of constitutive peptidases in latex sap in addition to inducible and de novo synthesized pathogenesis-related proteins (PR-proteins), raises the question about the role that each sap component plays to protect plants and how synergism occurs among sap proteins in the course of herbivory or infection. Here we discuss a variety of functions for laticifer and latex in plant defense. We propose that latex peptidases build the front line of defense against herbivores or pathogens.

Proteomic identification and purification of seed proteins from native Amazonian species displaying antifungal activity

Seeds of native species from the rain forest (Amazon) are source of chitinases and their protein extracts exhibited strong and broad antifungal activity. Numerous plant species native to the Amazon have not yet been chemically studied. Studies of seeds are scarcer, since adversities in accessing study areas and seasonality pose constant hurdles to systematic research. In this study, proteins were extracted from seeds belonging to endemic Amazon species and were investigated for the first time. Proteolytic activity, peptidase inhibitors, and chitinases were identified, but chitinolytic activity predominated. Four proteins were purified through chromatography and identified as lectin and chitinases by MS/MS analyses. The proteins were examined for inhibition of a phytopathogen (Fusarium oxysporum). Analyses by fluorescence microscopy suggested binding of propidium iodide to DNA of fungal spores, revealing that spore integrity was lost when accessed by the proteins. Further structural and functional analyses of defensive proteins belonging to species facing highly complex ecosystems such as Amazonia should be conducted, since these could provide new insights into specificity and synergism involving defense proteins of plants submitted to a very complex ecosystem.

Molecular cloning and anti-invasive activity of cathepsin L propeptide-like protein from Calotropis procera R. Br. against cancer cells

Cathepsin L of cancer cells has been shown to play an important role in degradation of extracellular matrix for metastasis. In order to reduce cell invasion, cathepsin L propeptide-like proteins which are classified as the I29 family in the MEROPS peptidase database were characterized from Calotropis procera R. Br., rich in cysteine protease. Of 19 candidates, the cloned and expressed recombinant SnuCalCp03-propeptide (rSnuCalCp03-propeptide) showed a low nanomolar K_i value of 2.3 ± 0.2 nM against cathepsin L. A significant inhibition of tumor cell invasion was observed with H1975, HT29, MDA-BM-231, PANC1, and PC3 with a 76, 67, 67, 63, and 79% reduction, respectively, in invasion observed in the presence of 400 nM of the rSnuCalCp03-propeptide. In addition, thermal and pH study showed rSnuCalCp03-propeptide consisting of secondary structures was stable at a broad range of temperatures (30–70 °C) and pH (2–10, except for 5 which is close to the isoelectric point of 5.2).

Antimicrobial evaluation of red, phytoalexin-rich sorghum food biocolorant

Sorghum (Sorghum bicolor) extract is traditionally used as red biocolorant in West Africa to colour foods, among which wagashi, a soft cheese. This biocolorant is a source of the phytoalexin apigeninidin and phenolic acids, and users claim that it has preservative effects next to its colouring properties. If such a claim can be scientifically substantiated, it adds a valuable functional property to this natural red colorant, thereby increasing its potential applications in the food industry. Hence, the present study evaluated the antimicrobial properties of dye sorghum extracts using challenge tests in broth and wagashi as a model of a popular food application. The alkaline extract and hot aqueous extract were used for dyeing wagashi by 87.7% and 12.3% of the traders, respectively. The dyeing procedure is perceived as a preservation strategy, and is also a means to maximise the revenues. However, results demonstrated that the application of sorghum biocolorant on wagashi had no inhibitory effect on the growth of fungi (Penicillium chrysogenum, Cladosporium macrocarpum) and Escherichia coli O157:H7. Furthermore, sorghum biocolorant in broth had no effect on growth of Listeria monocytogenes and Escherichia coli O157:H7. Consequently, the commonly used extracts for colouring soft West-African cheese did not show a preservative effect. In addition, dyeing did not affect the physico-chemical properties of wagashi. Still, the red colour hampered visual detection of microbial growth, thus clarifying the preservative effect reported by users.

Dairy curd coagulated by a plant extract of Calotropis procera: Role of fat structure on the chemical and textural characteristics

Milk is often subjected to technological treatments which have impacts on the structure of milk constituents and the characteristics of rennet curds. In this paper, the influence of the dairy fat structure on the biochemical and textural characteristics of curds coagulated by an extract of Calotropis procera leaves was studied. Standardized milks were reconstituted with the same contents in protein (35g·kg^-1) and fat (35g·kg^-1) but with different structures of fat i.e. homogenized anhydrous milk fat (HAMF), homogenized cream (HC) and non-homogenized cream (NHC). As expected, the size distributions of fat globules in the different milks were different. After their coagulations by the plant extract, the physico-chemical characteristics of the curds and respective wheys were determined. No difference was observed in the coagulation time between the three milks but the whey removed more quickly from HAMF and HC curds than NHC-curd. The biochemical analyses of curds revealed a lower content in dry matter and fat in the NHC-curd compared to HAMF- and HC-curds. Otherwise, the NHC-whey exhibited the highest amount of fat. Observations by confocal microscopy showed that the fat globules were homogenously distributed and well trapped in the protein networks of HAMF- and HC-curds. In the NHC-curd, the fat globules were located in whey pockets, with less connectivity with the protein network. The textural analysis showed that the NHC-curd was more elastic, soft and adhesive than HAMF- and HC-curds. Homogenization significantly reduced the loss of fat during cheese manufacturing and conferred specific textural characteristics to the curds coagulated by an extract of Calotropis procera.

The osmotin of Calotropis procera latex is not expressed in laticifer-free cultivated callus and under salt stress

The latex of Calotropis procera has previously been reported to contain osmotin. This protein (CpOsm) inhibited phytopathogens and this was mechanistically characterized. Here, the time-course profile of CpOsm transcripts was examined in the salt-stressed cultivated callus of C. procera in order to better understand its role in the physiology of the plant. Stressed callus (80 mM NaCl) showed an unbalanced content of organic compounds (proline and total soluble sugar) and inorganic ions (Na⁺, Cl^-, and K⁺). Under salt treatment, the transcripts of CpOsm were detected after 12 h and slightly increased to a maximum at day seven, followed by reduction. Interestingly, CpOsm was not detected in the soluble protein fraction recovered from the salt-stressed callus as probed by electrophoresis, dot/Western blotting and mass spectrometry. The results suggested that (1) CpOsm is not constitutive in cultivated cells (laticifer-free tissues); (2) CpOsm transcripts appear under salt-stressed conditions; (3) the absence of CpOsm in the protein fractions of stressed cultivated cells indicated that salt-induced transcripts were not used for protein synthesis and this accounts to the belief that CpOsm may be a true laticifer protein in C. procera. More effort will be needed to unveil this process. In this study we show evidences that CpOsm gene is responsive to salt stress. However the corresponding protein is not produced in cultivated cells. Therefore, presently the hypothesis that CpOsm is involved in abiotic stress is not fully supported.

Identification and characterization of two germin-like proteins with oxalate oxidase activity from Calotropis procera latex

Germin-like proteins (GLPs) have been identified in several plant tissues. However, only one work describes GLP in latex fluids. Therefore, the goal of this study was to investigate GLPs in latex and get new insights concerning the structural and functional aspects of these proteins. Two complete sequences with high identity (>50%) with other GLPs, termed CpGLP1 and CpGLP2, were obtained and consecutively presented 216 and 206 amino acid residues, corresponding to molecular masses of 22.7 and 21.7kDa, pI 6.8 and 6.5. The three-dimensional models revealed overall folding similar to those reported for other plant GLPs. Both deduced sequences were grouped into the GER 2 subfamily. Molecular docking studies indicated a putative binding site consisting of three highly conserved histidines and a glutamate residue, which interacted with oxalate. This interaction was later supported by enzymatic assays. Superoxide dismutase (common activity in GLPs) was not detected for CpGLP1 and CpGLP2 by zymogram. The two proteins were detected in the latex, but not in non-germinated or germinated seeds and calli. These results give additional support that germin-like proteins are broadly distributed in plants and they are tissue-specific. This particularity deserves further studies to better understand their functions in latex.

Physico-chemical characterization of dairy gel obtained by a proteolytic extract from Calotropis procera - A comparison with chymosin

Chymosin is the major enzyme used in cheesemaking but latex enzymes are also used. The aim of this work was to characterize the composition and the structure of dairy gel obtained by an extract of Calotropis procera leaves in comparison with those obtained by chymosin. The biochemical and mineral compositions of the curds and the cheese yields obtained by using Calotropis procera extract or chymosin were relatively similar. Quantitative and qualitative evaluations of proteolysis after milk coagulation, determined by the non-protein nitrogen content and chromatography coupled to mass spectrometry, indicated that Calotropis procera extract was more proteolytic than chymosin and that κ-casein was proteolyzed. The main consequence of proteolysis by Calotropis procera extract or chymosin was the formation of a similar and regular network with the presence of aggregates of casein micelles. These results support that Calotropis procera extract can be used as effective coagulant in cheesemaking.

First insights into the diversity and functional properties of chitinases of the latex of Calotropis procera

Chitinases (EC 3.2.1.14) found in the latex of Calotropis procera (Ait) R. Br. were studied. The proteins were homogeneously obtained after two ion exchange chromatography steps. Most proteins were identified individually in 15 spots on 2-D gel electrophoresis with isoelectric points ranging from 4.6 to 6.0 and molecular masses extending from 27 to 30 kDa. Additionally, 66 kDa proteins were identified as chitinases in SDS-PAGE. Their identities were further confirmed by mass spectrometry (MS) analysis of the tryptic digests of each spot and MS analysis of the non-digested proteins. Positive reaction for Schiff's reagent suggested the proteins are glycosylated. The chitinases exhibited high catalytic activity toward to colloidal chitin at pH 5.0, and this activity underwent decay in the presence of increasing amounts of reducing agent dithiothreitol. Spore germination and hyphae growth of two phytopathogenic fungi were inhibited only marginally by the chitinases but were affected differently. This suggested a complex relationship might exist between the specificity of the proteins toward the fungal species. The chitinases showed potent insecticidal activity against the Bruchidae Callosobruchus maculatus, drastically reducing survival, larval weight and adult emergence. It is concluded that closely related chitinases are present in the latex of C. procera, and the first experimental evidence suggests these proteins are involved more efficiently in defence strategies against insects rather than fungi.

Chemical composition and in vitro activity of Calotropis procera (Ait.) latex on Haemonchus contortus

Calotropis procera is among the species of medicinal plants that have traditionally been used for the treatment of parasites in small ruminants, stimulating the scientific validation of anthelmintic effects. This study aimed to investigate the chemical composition of ethyl acetate extract of Calotropis procera latex (EAECPL), assess the in vitro effect against Haemonchus contortus and the structural changes caused in the adult worm. The latex was collected, lyophilized and subjected to washing with the ethyl acetate solvent to obtain EAECPL. The constituents of the extract were isolated by column chromatography and identified by (13)C and (1)H nuclear magnetic resonance spectroscopy. The egg hatching test (EHT), larval development test (LDT) and adult worms motility test (WMT) were conducted to evaluate the effectiveness of EAECPL on eggs, larvae and adult of H. contortus, respectively. The worms obtained from the WMT, after 24h exposure to EAECPL or controls were observed on a scanning electron microscope (SEM). The results were analysed by variance analysis and compared with Tukey's test (P<0.05). Three compounds were isolated from EAECPL and identified as urs-19(29)-en-3-yl acetate, (3β)-Urs-19(29)-en-3-ol, and 1-(2',5'-dimethoxyphenyl)-glycerol. In the EHT, EAECPL inhibited larval hatching by 91.8% at dose of 4mg/ml. In the LDT 1mg/ml inhibited 99.8% larval development. In the WMT, EAECPL in the concentration of 100μg/ml inhibited 100% motility of worms, 12h post-exposition. In the SEM, obvious differences were not detected between the negative control worms and the worms treated with EAECPL. In this study, EAECPL showed an effect on inhibition egg hatching, larval development and motility of the adult worms of H. contortus. This should be related both to the identified compounds, as well as the other compounds present in the EAECPL, acting alone or synergistically.

Protective Effect of High Molecular Weight Protein Sub-fraction of Calotropis procera Latex in Monoarthritic Rats

Background:

Proteins present in the latex of Calotropis procera have been shown to produce anti-inflammatory effect and to afford protection in various disease models.

Objectives:

To determine the efficacy of high molecular weight protein sub-fraction (LP_PI) of latex of C. procera in ameliorating joint inflammation and hyperalgesia in a preclinical model of arthritis.

Materials and Methods:

Monoarthritis was induced in rats by intra-articular injection of Freund's complete adjuvant (FCA) and the effect of two doses of LP_PI (5 and 25 mg/kg) and diclofenac (5 mg/kg) was evaluated on joint swelling, stair climbing ability, motility, and dorsal flexion pain on day 3. The rats were sacrificed on day 3 to measure tissue levels of reduced glutathione (GSH) and thiobarbituric acid reactive substances (TBARS). Evaluation of joint histology was also made.

Results:

Intra-articular injection of FCA produced joint swelling and difficulty in stair climbing ability, motility, and pain on flexion of the joint as revealed by scores obtained for these functional parameters. LP_PI produced a dose-dependent decrease in joint swelling and improved joint functions. Arthritic rats also revealed altered oxidative homeostasis where joint tissue GSH levels were decreased and TBARS levels were increased as compared to normal rats. The levels of these oxidative stress markers were near normal in arthritic rats treated with LP_PI. Moreover, treatment with LP_PI also maintained the structural integrity of the joint. The protective effect of LP_PI was comparable to the standard anti-inflammatory drug, diclofenac.

Conclusion:

The findings of the present study show that LP_PI fraction comprising high molecular weight proteins could be used for the alleviation of arthritic symptoms.

SUMMARY

High molecular weight protein sub-fraction of latex of Calotropis procera (LP_PI) reduced joint swelling and hyperalgesia in arthritic rats

LP_PI produced a significant improvement in stair climbing ability and motility in arthritic rats

LP_PI normalized the levels of oxidative stress markers in the arthritic joints

Treatment with LP_PI reduced neutrophil influx and edema in the arthritic joints

Abbreviations used: FCA: Freund's complete adjuvant, GSH: Glutathione, TBARS: Thiobarbituric acid reactive substances, TBA: Thiobarbituric acid, MDA: Malondialdehyde, LP_PI: Latex protein fraction PI.

New constitutive latex osmotin-like proteins lacking antifungal activity

Proteins that share similar primary sequences to the protein originally described in salt-stressed tobacco cells have been named osmotins. So far, only two osmotin-like proteins were purified and characterized of latex fluids. Osmotin from Carica papaya latex is an inducible protein lacking antifungal activity, whereas the Calotropis procera latex osmotin is a constitutive antifungal protein. To get additional insights into this subject, we investigated osmotins in latex fluids of five species. Two potential osmotin-like proteins in Cryptostegia grandiflora and Plumeria rubra latex were detected by immunological cross-reactivity with polyclonal antibodies produced against the C. procera latex osmotin (CpOsm) by ELISA, Dot Blot and Western Blot assays. Osmotin-like proteins were not detected in the latex of Thevetia peruviana, Himatanthus drasticus and healthy Carica papaya fruits. Later, the two new osmotin-like proteins were purified through immunoaffinity chromatography with anti-CpOsm immobilized antibodies. Worth noting the chromatographic efficiency allowed for the purification of the osmotin-like protein belonging to H. drasticus latex, which was not detectable by immunoassays. The identification of the purified proteins was confirmed after MS/MS analyses of their tryptic digests. It is concluded that the constitutive osmotin-like proteins reported here share structural similarities to CpOsm. However, unlike CpOsm, they did not exhibit antifungal activity against Fusarium solani and Colletotrichum gloeosporioides. These results suggest that osmotins of different latex sources may be involved in distinct physiological or defensive events.

A novel form of ficin from Ficus carica latex: Purification and characterization

A novel ficin form, named ficin E, was purified from fig tree latex by a combination of cation-exchange chromatography on SP-Sepharose Fast Flow, Thiopropyl Sepharose 4B and fplc-gel filtration chromatography. The new ficin appeared not to be sensitive to thiol derivatization by a polyethylene glycol derivative, allowing its purification. The protease is homogeneous according to PAGE, SDS-PAGE, mass spectrometry, N-terminal micro-sequencing analyses and E-64 active site titration. N-terminal sequencing of the first ten residues has shown high identity with the other known ficin (iso)forms. The molecular weight was found to be (24,294±10)Da by mass spectrometry, a lower value than the apparent molecular weight observed on SDS-PAGE, around 27 kDa. Far-UV CD data revealed a secondary structure content of 22% α-helix and 26% β-sheet. The protein is not glycosylated as shown by carbohydrate analysis. pH and temperature measurements indicated maxima activity at pH 6.0 and 50 °C, respectively. Preliminary pH stability analyses have shown that the protease conserved its compact structure in slightly acidic, neutral and alkaline media but at acidic pH (<3), the formation of some relaxed or molten state was evidenced by 8-anilino-1-naphtalenesulfonic acid binding characteristics. Comparison with the known ficins A, B, C, D1 and D2 (iso)forms revealed that ficin E showed activity profile that looked like ficin A against two chromogenic substrates while it resembled ficins D1 and D2 against three fluorogenic substrates. Enzymatic activity of ficin E was not affected by Mg(2+), Ca(2+) and Mn(2+) at a concentration up to 10mM. However, the activity was completely suppressed by Zn(2+) at a concentration of 1mM. Inhibitory activity measurements clearly identified the enzyme as a cysteine protease, being unaffected by synthetic (Pefabloc SC, benzamidine) and by natural proteinaceous (aprotinin) serine proteases inhibitors, by aspartic proteases inhibitors (pepstatin A) and by metallo-proteases inhibitors (EDTA, EGTA). Surprisingly, it was well affected by the metallo-protease inhibitor o-phenanthroline. The enzymatic activity was however completely blocked by cysteine proteases inhibitors (E-64, iodoacetamide), by thiol-blocking compounds (HgCl2) and by cysteine/serine proteases inhibitors (TLCK and TPCK). This is a novel ficin form according to peptide mass fingerprint analysis, specific amidase activity, SDS-PAGE and PAGE electrophoretic mobility, N-terminal sequencing and unproneness to thiol pegylation.

Crystallization and preliminary X-ray analysis of four cysteine proteases from Ficus carica latex

The latex of the common fig (Ficus carica) contains a mixture of at least five cysteine proteases commonly known as ficins (EC 3.4.22.3). Four of these proteases were purified to homogeneity and crystals were obtained in a variety of conditions. The four ficin (iso)forms appear in ten different crystal forms. All diffracted to better than 2.10 Å resolution and for each form at least one crystal form diffracted to 1.60 Å resolution or higher. Ficin (iso)forms B and C share a common crystal form, suggesting close sequence and structural similarity. The latter diffracted to a resolution of 1.20 Å and belonged to space group P3₁21 or P3₂21, with unit-cell parameters a = b = 88.9, c = 55.9 Å.

Cysteine Protease Profiles of the Medicinal Plant Calotropis procera R. Br. revealed by de novo transcriptome analysis

Calotropis procera R. Br., a traditional medicinal plant in India, is a promising source of commercial proteases, because the cysteine proteases from the plant exhibit high thermo-stability, broad pH optima, and plasma-clotting activity. Though several proteases such as Procerain, Procerain B, CpCp-1, CpCp-2, and CpCp-3 have been isolated and characterized, the information of their transcripts is limited to cDNAs encoding their mature peptides. Due to this limitation, in this study, to determine the cDNA sequences encoding full open reading frame of these cysteine proteases, transcripts were sequenced with an Illumina Hiseq2000 sequencer. A total of 171,253,393 clean reads were assembled into 106,093 contigs with an average length of 1,614 bp and an N50 of 2,703 bp, and 70,797 contigs with an average length of 1,565 bp and N50 of 2,082 bp using Trinity and Velvet-Oases software, respectively. Among these contigs, we found 20 unigenes related to papain-like cysteine proteases by BLASTX analysis against a non-redundant NCBI protein database. Our expression analysis revealed that the cysteine protease contains an N-terminal pro-peptide domain (inhibitor region), which is necessary for correct folding and proteolytic activity. It was evident that expression yields using an inducible T7 expression system in Escherichia coli were considerably higher with the pro-peptide domain than without the domain, which could contribute to molecular cloning of the Calotropis procera protease as an active form with correct folding.

Peptidases and peptidase inhibitors in gut of caterpillars and in the latex of their host plants

Studies investigating the resistance-susceptibility of crop insects to proteins found in latex fluids have been reported. However, latex-bearing plants also host insects. In this study, the gut proteolytic system of Pseudosphinx tetrio, which feeds on Plumeria rubra leaves, was characterized and further challenged against the latex proteolytic system of its own host plant and those of other latex-bearing plants. The gut proteolytic system of Danaus plexippus (monarch) and the latex proteolytic system of its host plant (Calotropis procera) were also studied. The latex proteins underwent extensive hydrolysis when mixed with the corresponding gut homogenates of the hosted insects. The gut homogenates partially digested the latex proteins of foreign plants. The fifth instar of D. plexippus that were fed diets containing foreign latex developed as well as those individuals who were fed diets containing latex proteins from their host plant. In vitro assays detected serine and cysteine peptidase inhibitors in both the gut homogenates and the latex fluids. Curiously, the peptidase inhibitors of caterpillars did not inhibit the latex peptidases of their host plants. However, the peptidase inhibitors of laticifer origin inhibited the proteolysis of gut homogenates. In vivo analyses of the peritrophic membrane proteins of D. plexippus demonstrate resistance against latex peptidases. Only discrete changes were observed when the peritrophic membrane was directly treated with purified latex peptidases in vitro. This study concludes that peptidase inhibitors are involved in the defensive systems of both caterpillars and their host plants. Although latex peptidase inhibitors inhibit gut peptidases (in vitro), the ability of gut peptidases to digest latex proteins (in vivo) regardless of their origin seems to be important in governing the resistance-susceptibility of caterpillars.

Proteinase activity in latex of three plants of the family Euphorbiaceae

In the family of Euphorbiaceae,the genera Euphorbia and Sapium are known to contain essentially latex-bearing species. In the present study, the latex of Euphorbia selloi(Klotzsch & Garcke) Boiss., Euphorbia papillosa A.St.-Hil., and Sapium glandulosum (L.) Morong, plants native from Brazil, were examined concerning proteolytic activity. All studied species have proteins with significant proteolytic activity and E. papillosa has the greatest specific activity. Aiming to verify the type of protease present, an assay with different inhibitors was performed. In the three tested plants, the proteolytic activity was significantly inhibited by a serine protease inhibitor 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride (AEBSF). Using techniques of electrophoresis with polyacrylamide gels (SDS-PAGE), the subunits of proteins were separated according to their molecular masses, and the protein activity was visually detected by zymography.