A polarizable ellipsoidal force field for halogen bonds

The anisotropic effects and short‐range quantum effects are essential characters in the formation of halogen bonds. Since there are an array of applications of halogen bonds and much difficulty in modeling them in classical force fields, the current research reports solely the polarizable ellipsoidal force field (PEff) for halogen bonds. The anisotropic charge distribution was represented with the combination of a negative charged sphere and a positively charged ellipsoid. The polarization energy was incorporated by the induced dipole model. The resulting force field is “physically motivated,” which includes separate, explicit terms to account for the electrostatic, repulsion/dispersion, and polarization interaction. Furthermore, it is largely compatible with existing, standard simulation packages. The fitted parameters are transferable and compatible with the general AMBER force field. This PEff model could correctly reproduces the potential energy surface of halogen bonds at MP2 level. Finally, the prediction of the halogen bond properties of human Cathepsin L (hcatL) has been found to be in excellent qualitative agreement with the cocrystal structures. © 2013 Wiley Periodicals, Inc.     

Cathepsin B-responsive nanodrug delivery systems for precise diagnosis and targeted therapy of malignant tumors

The tumor microenvironment (TME) significantly influences cancer evolution and therapeutic efficacy. Targeting biofunctional molecules to the TME has long been appreciated as a means of raising local drug concentrations and reducing systemic toxicities. The booming nanotechnology field has realized the importance of cathepsin B to derive a variety of intelligent enzyme-responsive nanosized drug delivery systems (nanoDDS) to improve treatment responses and clinical outcomes. In this tutorial review, after introducing the molecular structure and physiological/pathological functions of cathepsin B, the outstanding achievements of cathepsin B-responsive nanoplatforms in the precise diagnosis, targeted therapy, and synergistic theranostics of malignant tumors are systematically described. Finally, the challenges of enzyme-substrate incompatibility, low diagnostic sensitivity, mass production and biocompatibility of multifunctional nanoDDS are considered in order to successfully promote them to clinical applications     

New approach for natural products screening by real-time monitoring of hemoglobin hydrolysis using quartz crystal microbalance

The hemoglobin (Hb) released from erythrocytes is a primary nutritive component for many blood-feeding parasites. The aspartic protease cathepsin D is a hemoglobinase that is involved in the Hb degradation process and is considered an interesting target for chemotherapy intervention. However, traditional enzymatic assays for studying Hb degradation utilize spectrophotometric techniques, which do not allow real-time monitoring and can present serious interference problems. Herein, we describe a biosensor using simple approach for the real-time monitoring of Hb hydrolysis as well as an efficient screening method for natural products as enzymatic inhibitors using a quartz crystal microbalance (QCM) technique. Hemoglobin was anchored on the quartz crystal surface using mixed self-assembled monolayers. The addition of the enzyme caused a mass change (frequency shift) due to Hb hydrolysis, which was monitored in real time. From the frequency change patterns of the Hb-functionalized QCM, we evaluated the enzymatic reaction by determining the kinetic parameters of product formation (k_cat). The QCM enzymatic assay using immobilized human Hb was shown to be an excellent approach for screening possible inhibitors in complex mixtures, opening up a new avenue for the discovery of novel inhibitors.     

Demonstration of a protein with enhanced resistance to proteinase K in transmissible cytopathic condition elicited by cell-free lysate of free-living ameba Naegleria gruberi

The cell-free lysate of free-living amebae Naegleria gruberi and Naegleria fowleri were reported to elicit cytopathic effect in various cell lines that could be indefinitely transmitted by the culture media. The causative agent showed sensitivity to treatments detrimental to proteins while resisted exposures damaging to nucleic acids. Here we demonstrate that subsequent to exposure to N. gruberi lysate mild digestion with proteinase K reveals the presence of a protein band in HeLa cells absent from control cell lines. Though the small quantity of this protein with enhanced resistance to proteinase K relative to the total protein content of the sample has proved to date insufficient for its purification, we suppose that it is a human cellular protein that assumed altered conformation in a prion-like fashion. The conformational conversion could have been trigerred by an ameba protein in the lysate. In addition, we showed that HeLa cells treated with N. gruberi lysate display elevated cathepsin B activity which is assumed to be a secondary response to the accumulation of the proteinase K-resistant protein. We propose that a number of degenerative sequelae following previous microbial infections in mammals could have a similar pathomechanism. Moreover, epidemiological data strongly suggest that natural prion disease in sheep, goat and cervids may also have an etiology linked to prior infection/colonization with a microbe, as it had already been proposed by one of us.     

Microplate assay for determination of cathepsin D activity based on quantification of a specific and stable peptide released from hemoglobin: VV-hemorphin-7

Cathepsins are key enzymes in mediating turnover of cytosolic proteins. In the context of cancer progression, those most actively studied include cathepsins D and B which have been implicated in processes such as growth and metastasis of many types of cancer. For more than 10 years, their roles as tumor marker and prognostic indicators have been studied, especially in breast cancer. Most of the studies relating the role of cathepsin D in cancer used immunological detection methods to determine the level of enzyme but do not reflect enzyme activity. Moreover, one of the problems in understanding cathepsin D clinical studies is that immunoassays may employ antibodies against the different form of the antigen. As an alternative, this work describes an indirect method to assess the active form of cathepsin D based on ELISA quantification of a specific and stable product of hemoglobin hydrolysis: VV-hemorphin-7. The procedure described here allows a low detection limit (ca. 5×10⁻⁹ M) and thus can represent an original approach to evaluate cathepsin D activity in biological samples.     

Cathepsin B-responsive nanodrug delivery systems for precise diagnosis and targeted therapy of malignant tumors

The tumor microenvironment (TME) significantly influences cancer evolution and therapeutic efficacy. Targeting biofunctional molecules to the TME has long been appreciated as a means of raising local drug concentrations and reducing systemic toxicities. The booming nanotechnology field has realized the importance of cathepsin B to derive a variety of intelligent enzyme-responsive nanosized drug delivery systems (nanoDDS) to improve treatment responses and clinical outcomes. In this tutorial review, after introducing the molecular structure and physiological/pathological functions of cathepsin B, the outstanding achievements of cathepsin B-responsive nanoplatforms in the precise diagnosis, targeted therapy, and synergistic theranostics of malignant tumors are systematically described. Finally, the challenges of enzyme-substrate incompatibility, low diagnostic sensitivity, mass production and biocompatibility of multifunctional nanoDDS are considered in order to successfully promote them to clinical applications.     

Catechu Inhibiting Cathepsin B Activity and Motility of HT1080 Cells

We reported that Catechu extract has a significant inhibitory effect on cathepsin B activity. The IC50 value for the Catechu extract against cathepsin B was 7.6 μg/mL. In addition, we showed that HT1080 human fibrosarcoma cells express cathepsin B and Catechu modulate the invasion and motility of these cells. These data may provide molecular mechanisms for the therapeutic effects of Catechu.     

Effect of high pressure on the reaction between bovine myofibrils and cathepsin D

This study deals with the effect of high pressure [50-500 MPa] and time of treatment [20-900 s] on the reaction between myofibrils and cathepsin D from bovine post mortem meat, using Surface Response Methodology. We shown that every high pressure treatment enhanced activity of cathepsin D as evaluated on haemoglobin as a substrate or on control meat myofibrils. We also put in evidence that cathepsin D could carry out the hydrolysis of high pressure treated myofibrils. At last we studied the action of pressurised cathepsin D on pressurised myofibrils, and proved that the hydrolysis was increasing up to 170 MPa and then decreased; above 300 MPa the activity was lower than with control cathepsin D and control myofibrils. Thus above 300 MPa recognition of natural substrate is affected by high pressure induced modifications. These results may help to explain why high pressure treatment of post rigor meat is not able to increase tenderness.     

组织蛋白酶K拟肽腈类抑制剂的合成、表征及抑制效应检测

针对组织蛋白酶K(Cat K)的活性位点的化学结构特征设计合成了一系列拟肽腈类抑制剂, 并检测了其抑制效果, 得到了高效且具有较高选择性的抑制剂(其中抑制剂b和f对Cat K的抑制常数Ki值分别为15.9和19.1 nmol/L). 构效关系分析表明, P2与P3位连接部分以及P3基团的结构不同可使其抑制效果产生100倍以上的差异.