Inactivation of Jack Bean Urease by Nitidine Chloride from Zanthoxylum nitidum: Elucidation of Inhibitory Efficacy, Kinetics and Mechanism

Structural and Functional Analysis of Urease Accessory Protein E from Vancomycin-Resistance Staphylococcus aureus MU50 Strain

BACKGROUND

An increasing prevalence of biofilm forming strains by vancomycinresistance Staphylococcus aureus (VRSA) is one of the most important causes of antimicrobial resistance. VRSA possesses various regulatory factors to form and sustain biofilm in biotic or abiotic conditions. Among them, ureolytic activity is an important factor in the stabilization of biofilms by neutralizing the acidic environment. Various urease accessory proteins are required to activate the urease enzyme inside the biofilm.

OBJECTIVE

To optimize the cloning, expression and purification of urease accessory protein E from VRSA for determination of the secondary structure, and functional characterization by using Berthelot's method.

METHODS

BAB58453.1 gene (which encodes possible urease accessory protein E), having 38% similarity to Bacillus pasteurii UreE protein, was cloned, expressed, and purified by single-step affinity chromatography for performing secondary structural studies using circular dichroism spectroscopy, and functional analysis using Berthelot's and crystal violet assay.

RESULTS

Structure elucidation using NMR and circular dichroism spectroscopy techniques revealed that UreE protein has a partially foldedα-helical structure. Using Berthelot's method, it was identified that the purified UreE protein has enhanced urease enzyme activity, in comparison to the control. From the results of Berthelot's and crystal violet assays, it was deduced that the selected gene (UreE protein) plays a key role in enhancing urease enzyme activity and contributes to biofilm stability.

CONCLUSION

Structural studies on VRSA urease accessory proteins could aid in the identification of new drug targets or the development of effective antibiofilm strategies (in combination with other drug targets) against infections caused by biofilm-producing strains.

Nitidine chloride, a benzophenanthridine alkaloid from Zanthoxylum nitidum (Roxb.) DC., exerts multiple beneficial properties, especially in tumors and inflammation-related diseases

Plant-derived alkaloids are a kind of very important natural organic compounds. Nitidine chloride is one of the main active ingredients in Zanthoxylum nitidum (Roxb.) DC. which is a frequently-used Chinese herbal medicine. Z. nitidum has many kinds of efficacy, such as activating blood circulation and removing stasis, promoting qi circulation and relieving pain, and detoxication and detumescence. In China, Z. nitidum is usually used for the treatment of gastrointestinal diseases, toothache, and traumatic injury. At present, there are numerous studies of nitidine chloride with regard to its pharmacology, pharmacokinetics, toxicology, etc. However, a systematic, cutting-edge review of nitidine-related studies is extremely lacking. The present paper aimed at comprehensively summarizing the information on the extraction, separation and purification, pharmacology, pharmacokinetics, toxicology and formulation of nitidine chloride. The knowledge included in the present study were searched from the following academic databases involving Web of Science, PubMed, Google scholar, Elsevier, CNKI and Wanfang Data, till July 2022. In terms of nitidine chloride extraction, enzymatic method and ultrasonic method are recommended. Resin adsorption and chromatography were usually used for the separation and purification of nitidine chloride. Nitidine chloride possesses diversified therapeutical effects, such as anti-tumor, anti-inflammation, anti-colitis, anti-malaria, anti-osteoporosis, anti-rheumatoid and so on. According to pharmacokinetics, the intestinal absorption of nitidine chloride is passive diffusion, and it is rarely excreted with urine and feces in the form of prototype drug. Nitidine chloride has a moderate binding to plasma protein, which is independent of the drug concentration. As to toxicology, nitidine chloride showed certain toxicity on liver, kidney and heart. Certain new formulations, such as nanoparticle, microsphere and nano-micelle, could increase the therapeutic effect and decrease the toxicity of nitidine chloride. Despite limitations such as poor solubility, low bioavailability and certain toxicity, nitidine chloride is still a promising natural alkaloid for drug candidates. Extensive and intensive exploration on nitidine chloride is essential to promote the usage of nitidine-based drugs in the clinic practice.

Sanguinarine, a major alkaloid from Zanthoxylum nitidum (Roxb.) DC., inhibits urease of Helicobacter pylori and jack bean: Susceptibility and mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum nitidum (Roxb.) DC. (Z. nitidum) is a traditional Chinese medicine and mainly adopted to treat gastric ulcer, gastritis and stomach cancer. Sanguinarine (SNG), a natural alkaloid isolated from Z. nitidum, possesses significant anti-Helicobacter pylori and gastric protection effects. However, the underlying mechanism is sparsely elucidated.

AIM OF THIS STUDY

The present study aims to explore the inhibition effect, kinetics and potential mechanism of SNG against H. pylori urease (HPU) and jack bean urease (JBU).

MATERIALS AND METHODS

The improved spectrophotometric berthelot method was applied to estimate the inhibitory effect of SNG against HPU and JBU. The Lineweaver-Burk plots were adopted for investigating the inhibitory pattern in enzymatic kinetics. Sulfydryl-containing compounds and competitive active-site Ni²⁺ binding depressors were used for mechanism research.

RESULTS

SNG remarkably suppressed the activities of HPU and JBU in concentration-and time-dependent mode with IC₅₀ of 0.48 ± 0.14 mM and 0.11 ± 0.02 mM, respectively, in comparison with urease retardant acetohydroxamic acid (0.06 ± 0.01 mM for HPU and 0.03 ± 0.00 mM for JBU, respectively). Kinetic analysis demonstrated that the inhibition of SNG against HPU and JBU were separately characterized by slow-binding, mixed-type and slow-binding, non-competitive type. Addition of sulfydryl-containing reagents (dithiothreitol, glutathione and L-cysteine) and competitive Ni²⁺ binding restrainers (boric acid and sodium fluoride) significantly abrogated the urease inhibitory effect of SNG, suggesting the significant role of the thiols and Ni²⁺ for the urease inhibition by SNG. By contrast, interaction with thiol groups possibly contributed to the repression of SNG on JBU. Furthermore, the urease suppression was proved to be partially reversible since the SNG-blocked enzyme could be partly reactivated by glutathione.

CONCLUSION

SNG could observably inhibit H. pylori urease targeting the thiols and Ni²⁺, which indicated that SNG was a new urease suppressant with great promise. The present research also provided scientific evidence for the application of SNG and Z. nitidum treating H. pylori-associated gastrointestinal diseases.

Development of urease inhibitors by fragment-based dynamic combinatorial chemistry

In this study, fragment-based dynamic combinatorial chemistry (DCC) was explored for the development of novel urease inhibitors. Based on a rationally designed fragment, two iteratively evolved dynamic combinatorial libraries (DCLs) were generated and screened in the presence of urease template. The best ligand identified revealed not only strong urease inhibition but also low cytotoxicity. Additionally, possible inhibitory mechanism was elucidated in the binding kinetic study and docking simulation.