Mini Reviews in Medicinal Chemistry - Volume 16, Issue 14, 2016

The role of halogen atoms in pharmaceutical compounds has been recently revised, due to the weak interaction through the so called “halogen bond” between small molecules and proteins or other biomacromolecules, which could be fundamental for binding at a particular site within the macromolecule. Moreover, thousands of natural halogenated compounds have been described to date, pointing to a functional role of halogen atoms in these compounds, as well as a diversity of halogenating enzymes involved in the synthesis of these halogenated metabolites. In this mini-review the different halogenases described to date are presented, particularly those catalyzing halogenation reactions with potential applications in the pharmaceutical field. Oxidative halogenases following an electrophilic halogenation mechanism are the oldest and best characterized halogenases; however, novel halogenases following a nucleophilic halogenation mechanism have been recently described. The catalytic properties as well as the selectivity of some of these enzymes can be modulated through protein engineering, both by single point mutations or by directed evolution; on the other hand, metabolic pathway engineering has been used to improve the production of halogenated metabolites, as well as to produce novel halogenated compounds, potentially important in the pharmaceutical field. Recent advances and prospective on the field of enzymatic halogenation are covered.

The enzyme human aromatase (HA), a member of the cytochrome P450 family, catalyses in a highly specific and peculiar manner the conversion of estrogens to androgens. Thus, this enzyme is a relevant target for inhibitor design for the treatment of breast cancer and currently there are several HA inhibitors employed in clinical practice. The HA crystal structure was solved only in 2009 and, since then, several studies have been done to characterize a variety of its structural, dynamical and mechanistic properties. In the last decade, the predictive power and the accuracy of computer simulations techniques, either relying on force field or on “ab initio” description of the system, has enormously increased. This was mainly due to the development of more accurate algorithms, which allow accelerating the time-scale accessible by simulations techniques, and to the increase of computer power. Hence, computer simulations can now accurately paint an atomistic picture to the molecular mechanism of biomolecules providing also an estimate of the kinetic and thermodynamic properties of the enzyme at increasingly quantitative level. In this review, on the basis of selected examples taken from our work, we summarize current active research topics concerning HA enzyme, with a focus on computational studies. In particular, we will illustrate current results and novel hypothesis concerning the final (rate-determining) aromatization step promoted by this enzyme, on how the structural/dynamics/functional properties of HA are modulated in a membrane lipophilic environment, and finally on novel possible (allosteric) inhibition mechanisms which may modulate estrogen production in HA.

A biosensor is a self-contained integrated device, which is capable of providing specific quantitative or semiquantitative analytical information using a biological (or biomimetic) recognition element, which is retained in direct spatial contact with an electrochemical transduction element. One of the main features of biosensors is the remarkable selectivity that their biological components confer on them. Enzymes are the most common and well-developed recognition system of the family known as catalytic biosensors. This mini-review is focused on enzyme-based biosensors for medical applications. In particular, the new trends for the technology are described. A special emphasis is devoted to the non-invasive and painless monitoring of body metabolites, such as glucose.

Epidermal Growth Factor Receptor (EGFR) is a transmembrane glycoprotein that constitutes one of the four members of ErbB family of tyrosine kinase receptors. Activation of EGFR leads to autophosphorylation of receptor tyrosine kinase that initiates a cascade of downstream signaling pathways involved in regulating cellular proliferation, differentiation, and survival. EGFR is abnormally activated by various mechanisms like receptor overexpression, mutation, ligand-dependent receptor dimerization, ligand-independent activation and is associated with the development of variety of human cancers. EGFR inhibition is one of the key targets for cancer chemotherapy. Approval of tyrosine kinase inhibitors such as erlotinib, gefitinib, and lapatinib for the treatment of non-small cell lung cancer led to tremendous development of novel EGFR inhibitors in the last decade. Diverse class of chemical compounds from the synthetic origin has been extensively studied. This review highlights the various classes of synthetically derived molecules which have been reported in the last few years as potential EGFR and EGFR/ErbB-2 dual inhibitors. A brief synthetic methodology to access these compounds has been highlighted along with the SAR. We strongly believe that this review will provide a platform to the synthetic chemists and biologists to design and synthesize new and potent compounds that inhibit EGFR and ErbB-2.

In recent years, metabolomics has become a necessary tool for understanding the impact of external and pathological factors on the operation of biological systems. The first reports of metabolomics date back to the 1970s, however, the area only began to develop dynamically at the beginning of this century and has proved effective only during the present decade. The five primary tools used in this form of analysis are NMR spectrometry, HPLC, TLC-UV, GC-MS and LC-MS/MS, with MS as the most universal approach, particularly when used together with chromatographic separation and NMR. Diabetes mellitus type 2 (T2DM) is a rapidly growing problem with global consequences. The metabolomic approach has been extensively applied to examining T2DM, insulin resistance and obesity, not only to assess the development of the disease, but also to discover its potential biomarkers. The presented review summarizes current studies on lipidomic and proteomic profiles in the context of different types of diabetes mellitus disease (T1DM, T2DM and GDM), as determined by chromatography-coupled mass spectrometry.

Histone deacetylase 6 (HDAC6) catalyses the removal of acetyl groups from the lysine residues of a series of non-histone proteins, e.g., α-tubulin, Hsp90 and cortactin. HDAC6 is a unique deacetylase enzyme that is related to various processes that may be important in oncological, immunological and neurological fields, which makes the study of selective inhibitors extremely important to understand the function of this enzyme and to validate HDAC6 as a drug target through the development of clinical candidates. Therefore, this review describes the structure-activity and structureselectivity relationships of HDAC6 inhibitors, which were divided into two main classes, bulky and lipophilic cap groups and inhibitors with phenyl linkers.