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Inappropriate activation of the Epidermal growth factor receptor (EGFR) group of kinases has been identified in a variety of tumour cells, either due to mutation or overexpression. Although the tumour is a fatal disease, significant therapy discoveries have lately been made. The human EGFR and this family of kinases have emerged as promising targets for cancer therapy. In this molecular docking study, Natural marine toxins are employed to regulate the activity of the human EGFR tyrosine kinase domain (EGFRtkd) in the molecular docking investigation (PDB ID5JEB). Marine biotoxins can cause neurological, gastrointestinal, and cardiovascular problems, as well as severe mortality and long-term morbidity in some situations. Because there is no antidote for any of the natural marine poisons, supportive care is the mainstay of treatment. Paralytic shellfish poisoning, in particular, and puffer fish poisoning, in particular, can result in death within hours of exposure to the poisons and may require immediate medical intervention. However, this research found that marine biotoxins can modulate EGFRtkd. Furthermore, homoyessotoxin was anticipated to be an EGFRtkd modulator with a binding affinity as -9.584 kcal/mol. To employ the homoyessotoxin in tumour therapies, further knowledge of natural marine biotoxins and further toxicological research is required.

Multicomponent reactions are extremely relevant in green chemistry. They offer better conditions than traditional synthesis and are, therefore, used for many organic modifications. Recently, the synthesis of polyhydroquinolines has received much attention for its high pharmacological potential. In the present study, a polyhydroquinoline derivative was synthesized without the use of catalysts or solvents. The results of nuclear magnetic resonance and infrared spectroscopy demonstrated that the molecule was successfully synthesized. The molecule presents significant results of antimicrobial activity for the bacteria tested in the serial dilution method. It also increased the clotting time by 25.66 seconds for the highest dose and 12.66 seconds for the other doses tested. Prior incubation with the dose of 125 mg reduced the thrombolytic activity to 73%. The 125, 100, and 50 mg doses previously incubated with Bothrops moojeni venom inhibited approximately 30% of the phospholipase activity. The molecule was also able to reduce the cytotoxicity induced by proteases significantly. In conclusion, the molecule presents several biological properties, which highlights its pharmaceutical potential.

Background Recently, the metabolite-likeness of the drug space has emerged and has opened a new possibility for exploring human metabolite-like candidates in drug discovery. However, the applicability of metabolite-likeness in drug discovery has been largely unexplored. Moreover, there are no reports on its applications for the repositioning of drugs to possible enzyme modulators, although enzyme-drug relations could be directly inferred from the similarity relationships between enzyme’s metabolites and drugs. Methods We constructed a drug-metabolite structural similarity matrix, which contains 1,861 FDA-approved drugs and 1,110 human intermediary metabolites scored with the Tanimoto similarity. To verify the metabolite-likeness measure for drug repositioning, we analyzed 17 known antimetabolite drugs that resemble the innate metabolites of their eleven target enzymes as the gold standard positives. Highly scored drugs were selected as possible modulators of enzymes for their corresponding metabolites. Then, we assessed the performance of metabolite-likeness with a receiver operating characteristic analysis and compared it with other drug-target prediction methods. We set the similarity threshold for drug repositioning candidates of new enzyme modulators based on maximization of the Youden’s index. We also carried out literature surveys for supporting the drug repositioning results based on the metabolite-likeness. Results In this paper, we applied metabolite-likeness to repurpose FDA-approved drugs to disease-associated enzyme modulators that resemble human innate metabolites. All antimetabolite drugs were mapped with their known 11 target enzymes with statistically significant similarity values to the corresponding metabolites. The comparison with other drug-target prediction methods showed the higher performance of metabolite-likeness for predicting enzyme modulators. After that, the drugs scored higher than similarity score of 0.654 were selected as possible modulators of enzymes for their corresponding metabolites. In addition, we showed that drug repositioning results of 10 enzymes were concordant with the literature evidence. Conclusions This study introduced a method to predict the repositioning of known drugs to possible modulators of disease associated enzymes using human metabolite-likeness. We demonstrated that this approach works correctly with known antimetabolite drugs and showed that the proposed method has better performance compared to other drug target prediction methods in terms of enzyme modulators prediction. This study as a proof-of-concept showed how to apply metabolite-likeness to drug repositioning as well as potential in further expansion as we acquire more disease associated metabolite-target protein relations. Electronic supplementary material The online version of this article (doi:10.1186/s12859-017-1637-5) contains supplementary material, which is available to authorized users.

Enzymatic catalyses are mediated by functional groups present in amino acid side chains. The amino acid side chains of enzymes that are frequently directly involved in enzyme catalytic processes include histidine, serine, cystein, lysine, glutamate, and aspartate. The active site of an enzyme is usually larger than the substrate, since in most cases the substrate is partially surrounded by the active site. The structure of an enzyme is required to stabilize the conformation of the active site for achieving enzymatic function.

The dimeric form of banana phosphofructokinase (PFK-II) was purified by polyethylene glycol and ammonium sulphate fractionations, Sepharose 6B molecular sieve and DEAE Sephacell ion exchange chromatography to 72-fold with a yield of 45%. Initial velocity studies suggested that the enzyme followed a sequential ordered reaction mechanism. Heat inactivation studies with substrate and effectors provided evidence for the formation of a stable enzyme-magnesium complex, strong binding of ATP to the enzyme and a comparatively weaker binding of the ATP-Mg complex. Kinetic studies under different experimental conditions strongly suggested (1) the Mg-ATP complex as the phosphorylation substrate, (2) free ATP as the regulator, (3) a dual role for Mg2+ as an activator of substrate as well as an enzyme modulator, and (4) ATP dependent formation of the enzyme-Mg2+ complex which modulated the interaction between fructose 6-phosphate and the enzyme.

Melatonin exerts oncostatic effects on different kinds of tumors, especially on hormone-dependent breast cancer. The general conclusion is that melatonin, in vivo, reduces the incidence and growth of chemically-induced mammary tumors in rodents, and, in vitro, inhibits the proliferation and invasiveness of human breast cancer cells. Both studies support the hypothesis that melatonin inhibits the growth of breast cancer by interacting with estrogen-signaling pathways through three different mechanisms: (a) the indirect neuroendocrine mechanism which includes the melatonin down-regulation of the hypothalamic-pituitary-reproductive axis and the consequent reduction of circulating levels of gonadal estrogens, (b) direct melatonin actions at tumor cell level by interacting with the activation of the estrogen receptor, thus behaving as a selective estrogen receptor modulator (SERM), and (c) the regulation of the enzymes involved in the biosynthesis of estrogens in peripheral tissues, thus behaving as a selective estrogen enzyme modulator (SEEM). As melatonin reduces the activity and expression of aromatase, sulfatase and 17beta-hydroxysteroid dehydrogenase and increases the activity and expression of estrogen sulfotransferase, it may protect mammary tissue from excessive estrogenic effects. Thus, a single molecule has both SERM and SEEM properties, one of the main objectives desired for the breast antitumoral drugs. Since the inhibition of enzymes involved in the biosynthesis of estrogens is currently one of the first therapeutic strategies used against the growth of breast cancer, melatonin modulation of different enzymes involved in the synthesis of steroid hormones makes, collectively, this indolamine an interesting anticancer drug in the prevention and treatment of estrogen-dependent mammary tumors.

There are increased levels of stage-specific embryonic antigens-3 and -1 (SSEA-3 and SSEA-1) globo-series glycolipids in male versus female DBA/2 and C57BL/6 kidneys, respectively. To determine what enzymatic steps may be responsible for these differences, the activity and properties of UDP-galactose:globoside galactosyltransferase were studied in male and female mouse kidney microsomes. This enzyme participates in the biosynthesis of galactosylgloboside, SSEA-3 glycolipid; the reaction product was identified by high performance thin-layer chromatography (HPTLC) immunostaining. In C57BL/6 mice, the specific activity of the enzyme, in the presence of CHAPS, was 2-fold greater in the male than that in the female. Optimum pH for the enzyme from both sexes was about 5.6, and Mn2+ was essential for maximal activity. Fifty percent of the male and female enzyme activity was lost after preincubating the microsomes for 1 min at 55 degrees C; thereafter, the enzyme from female microsomes had a slower rate of denaturation. The Km for globoside in presence of sodium cholate for both male and female was 0.035 mM, but it was approximately 2-fold greater for the female in presence of CHAPS. The enzyme in male and female microsomes was differentially activated by CHAPS and cholate. The results suggest the presence of an enzyme modulator in these membranes. In DBA/2 mice, the enzyme activity was about 2-fold greater in males than that in the female. The specific activity of the enzyme in the two strains was of a similar magnitude.(ABSTRACT TRUNCATED AT 250 WORDS)

A gold nanoparticle functionalized with substrates for alpha-chymotrypsin was fabricated to afford an enzyme modulator that exhibited enzyme-specific activation coupled with general inhibition of other proteases.

Fluoride is widely used as an anticaries agent in drinking water and a variety of other vehicles. This use has resulted in major health benefits. However, there are still open questions regarding the mechanisms of anticaries action and the importance of antimicrobial effects in caries reduction. Fluoride acts in multiple ways to affect the metabolism of cariogenic and other bacteria in the mouth. F(-)/HF can bind directly to many enzymes, for example, heme-containing enzymes or other metalloenzymes, to modulate metabolism. Fluoride is able also to form complexes with metals such as aluminum or beryllium, and the complexes, notably AlF(4)(-) and BeF(3)(-).H(2)O, can mimic phosphate with either positive or negative effects on a variety of enzymes and regulatory phosphatases. The fluoride action that appears to be most important for glycolytic inhibition at low pH in dental plaque bacteria derives from its weak-acid properties (pK(a)=3.15) and the capacity of HF to act as a transmembrane proton conductor. Since many of the actions of fluoride are related to its weak-acid character, it is reasonable to compare fluoride action to those of organic weak acids, including metabolic acids, food preservatives, non-steroidal anti-inflammatory agents and fatty acids, all of which act to de-energize the cell membrane by discharging DeltapH. Moreover, with the realization that the biofilm state is the common lifestyle for most microorganisms in nature, there is need to consider interactions of fluoride and organic weak acids with biofilm communities. Hopefully, this review will stimulate interest in the antimicrobial effects of fluoride or other weak acids and lead to more effective use of the agents for disease control and other applications.

1. 1. Enzyme modulator mediated immunoassay (EMMIA) is a separation-free (homogeneous) enzyme amplified immunoassay. 2. 2. The assay is based on the ability of an analyte labeled enzyme modulator to modify the activity of an indicator enzyme and on ability of an anti-analyte antibody to abrogate the modifying action of the analyte-labeled enzyme modulator upon its binding to anti-analyte antibody. 3. 3. The principle of EMMIA is elaborated in detail. The stages in the development of an EMMIA are described. 4. 4. Criteria in selecting enzymes and modulators suitable for EMMIA are discussed. 5. 5. Examples of EMMIA's using different kinds of modulators for different classes of analytes are presented.

Enzyme Mediated Immunoassay: An Overview.- Separation-Free (Homogeneous) Enzyme Mediated Immunoassays.- Separation-Free Enzyme Immunoassay for Haptens.- Enzyme Modulator as Label in Separation-Free Immunoassays: Enzyme Modulator Mediated Immunoassay (EMMIA).- Prosthetic Group Labeled Enzyme Immunoassay.- Fluorogenic Substrate Labeled Separation-Free Enzyme Mediated Immunoassays for Haptens and Macromolecules.- Immunoassays Based on Conformational Restriction of the Enzyme Label Induced by the Antibody.- Nonseparation Enzyme Immunoassays for Macromolecules.- Liposome-Entrapped Enzyme Mediated Immunoassays.- Test Strip Enzyme Immunoassay.- Separation-Free Enzyme Fluorescence Immunoassay by Continuous Flow Injection Analysis.- Seperation-Required (Heterogenous) Enzyme Immunoassay.- Separation-Required (Heterogeneous) Enzyme Immunoassay for Haptens and Antigens.- Enzyme Immunoassay of Antibody.- The Amplified Enzyme-Linked Immunosorbent Assay (a-ELISA).- Affinity Column Mediated Immunoenzymetric Assays.- Steric Hindrance Enzyme Immunoassay (SHEIA).- Maleimide Derivative of Hapten for Enzyme Coupling in EIA.- Enzyme Immunoassay Using Tagged Enzyme-Ligand Conjugates.- Fluorimetric Measurements in Enzyme Immunoassays.- Radial Partition Enzyme Immunoassay.- Development of Immunochemical Enzyme Assays for Cardiac Isoenzymes.- Enzyme-Linked Immunoelectrotransfer Blot (EITB).- Enzyme Immunoassays for Tropical Parasitic Diseases.- Monoclonal Antibodies in Immunoenzymetric Assays.- The Ngo-Lenhoff (MBTH-DMAB) Peroxidase Assay.- Immunoperoxidase Techniques Using the Avidin-Biotin System.- Contributors.

Separation-free enzyme immunoassays for both haptens and macromolecules have been developed by using enzyme modulator as the label (Ngo and Lenhoff, 1980; Ngo, 1983; Finley et al., 1980; Place et al., 1983; Blecka et al., 1983; Bacquet and Twumasi, 1984; Brontman and Meyerhoff, 1984; Dona, 1985). In this chapter, enzyme modulators are defined as compounds capable of bringing about the modifications of the catalytic activity of an enzyme by inhibiting or enhancing (activating) the enzyme activity. The modification of an enzyme activity by enzyme modulators can be achieved through either noncovalent or covalent interactions between the enzyme and its modulators. Non-covalently interacting modulators are generally reversible modulators, such as reversible low molecular weight enzyme inhibitors (Webb, 1963) or enzyme activators (Wong, 1975), allosteric effectors (Stadtman, 1970), transition state analogs (Wolfenden, 1972; Lienhard, 1973; Ngo and Tunnicliff, 1981) and inhibitory antibodies to an enzyme (Marucci and Mayer, 1955; Visek et al., 1967; Cinader, 1976; Arnon, 1977). Covalently interacting enzyme modulators consist of irreversible modulators such as activesite directed irreversible enzyme inhibitors (Baker, 1967; Shaw, 1980), mechanism based inhibitors (Rando, 1974; Abeles, 1978) and enzyme mediated modification of enzyme activity (Krebs, 1972).

Enzyme modulator mediated immunoassay (EMMIA) is a separation-free enzyme amplified immunoassay. The assay uses an enzyme modulator (M) as the tag to label a ligand analyte (L). Such stable covalent enzyme modulator-ligand conjugates (M-L) is capable of modulating the activity of an indicator enzyme by either causing a significant inhibition of the enzyme activity or a dramatic activation.

A homogeneous enzyme immunoassay (EIA) based on the immunomodulation of an avidin-ligand conjugate and the inhibition of pyruvate carboxylase is described. The conjugation of the ligand, 5,5-diphenylhydantoin (DPH), to avidin does not affect avidin's capacity to bind biotin or inhibit pyruvate carboxylase. The DPH-avidin conjugate and free DPH were shown to compete for a limited number of antibody sites. The interaction of anti-DPH with the DPH-avidin conjugate sterically inhibited enzyme inactivation. Enzyme activity was correlated with DPH concentrations in the therapeutic range found in serum.