Current Organic Chemistry - Volume 20, Issue 11, 2016

The most effective approach in controlling infectious diseases and other immune related disorders has been the development and the extensive use of preventive vaccines and vaccine therapies. However, we still need effective vaccines against some of the most threatening infectious agents. The standard costs and approaches in developing and producing a vaccine are dramatically high. In the recent past, the common effort of scientists resulted in novel approaches to vaccine target identification largely based on bioinformatics, immunoinformatics and structural biology, reducing time to identification of relevant antigens. These strategies, together with an increased knowledge of host-pathogen interactions and protection mechanisms, is enhancing the rapid development of novel vaccines. The reverse vaccinology approach also allowed the development of a large number of new recombinant protein-based vaccines. However, this approach results poorly efficient against genetically complex diseases, such as malaria, tuberculosis, HIV, and towards cancer. In the latter cases, the modern approach for designing efficient vaccines is moving to structure vaccinology. The deep characterization of different epitopes permits the rational design of new immunogenic products. For example, new products obtained by combination of differently defined antigens, such as chimeric proteins, were proposed as improved vaccines against tuberculosis. Similarly, the structural characterization of antigenic oligosaccharides allowed the development of a commercial vaccine for the prevention of Haemophilus influenzae type B. This approach has also been proposed for the treatment of other infectious diseases, such as meningococcal infections, pneumococcal infections and tuberculosis as well as for the treatment of certain types of cancer.

Coupling of a macromolecule such as an enzyme or a receptor to a chromatographic support has revealed a powerful analytical tool to face different aspects related to drug discovery. Chromatographic systems with immobilized macromolecules have been developed to be used for different applications in pharmaceutical analysis including enzyme inhibitor screening, biopharmaceutics structural analysis, chiral separations and binding studies. These areas of research are very challenging both for the technological and for the applicative aspects. This review offers an overview of general strategies and references that can be considered in order to develop innovative and reliable “protein-labs” for specific separative analytical applications of pharmaceutical interest.

Hydrolases are versatile enzymes for synthetic purposes as they are able to catalyze multiple transformations in both aqueous medium and organic solvents. Their easiness of use and lack of cofactor dependency have attracted the attention of many organic chemists, which have successfully applied this family of enzymes in hydrolytic and reverse synthetic reactions. In this review, the authors have focused on the recent application of hydrolases for the synthesis of active pharmaceutical ingredients and different families of compounds with exceptional biological profiles. Thus, their action has been classified in non-selective and selective transformations including regio- and stereoselective processes. Asymmetric transformations are presented as key issues for the production of drug enantiomers, so examples of hydrolase-catalyzed kinetic resolutions, dynamic kinetic resolutions and desymmetrizations will be extensively discussed, presenting hydrolases as very versatile enzymes for the development of scalable synthetic transformations towards pharmaceuticals.

Industrial chemical companies have taken advantage of enzymes for the production of pharmaceuticals by means of nonselective and selective transformations. This review covers recently published chemoenzymatic synthesis of important drugs, focusing on the production of the desired targets with high to excellent yields. Remarkably, biocatalysts have allowed the development of asymmetric processes through different strategies, providing efficient access to challenging substrates that are difficult to obtain by traditional chemical methods. Thus, the action of different classes of non hydrolytic enzymes has been covered, including a wide number of oxidoreductases, lyases and transferases. The importance of using enzymes with synthetic purposes under mild reaction conditions is fully demonstrated in the production of active pharmaceutical ingredients and other organic compounds with interesting biological profiles.

D-amino acids are essential components of the bacterial cell wall and play notable roles in microbiology as regulators, for example in sporulation, biofilm formation or interspecies communication. Racemases are the specific enzymes catalyzing the interconversion of L-amino acids to D-amino acids. While most of racemases are mono-specific, a family of broad-spectrum racemases that can racemize ten of the 19 natural chiral amino acids has been recently reported. These enzymes can interconvert radically different residues such as aliphatic and positively charged residues producing non-canonical D-amino acids. Crystal structures together with bioinformatics allowed identification of the residues defining the molecular footprint in broad-spectrum racemases, the specific features of their active sites and the structural basis of their promiscuity. Here we review the recent knowledge on this family compared with the well established of alanine racemases. This structural information is a prerequisite for the development of novel drugs against the important human pathogens for which broadspectrum racemases play a key role.

Chemical modification of proteins with bioorthogonal reaction and site-selectivity has been increasingly recognized for exquisite control over homogeneity and geometry, allowing more complex and various applications of proteins. The development of novel bioorthogonal reactions and their adaptation to protein chemistry in the form of genetically encoded non-natural amino acids are fueling widespread use of the so-called ‘bioorthogonal protein conjugation’. Site-specific incorporation of a non-natural amino acid technique precisely delivers a bioorthogonal group to any defined site in response to an expanded genetic code where a selective bond-forming reaction equips proteins with novel functionalities in a chemically well-defined and homogeneous manner.

The aldol reactions catalyzed by aldolases are an important tool in the synthesis of different products or building blocks. However, despite its advantages, aldolases, as enzymes, have some troubles as their low activity against synthetic substrates or the low stability, doing difficult their application. There are different tools to improve the properties of this enzyme such as directed mutagenesis, directed evolution or the immobilization methods. The immobilization not only is able to improve the properties of the enzymes but also permits the reuse of the catalysts. This review is focused on the immobilization of different aldolases using different methodologies.

Magnetic nanoparticles (MNPs), in particular those based on iron oxides, have attracted a lot of attention during the last years for their applications in nanomedicine. This is due to their unique physicochemical properties, such as good biocompatibility, their size in the nanoscale and their superparamagnetism, making them useful for drug delivery, MRI, magnetic targeting and magnetic fluid hyperthermia. Due to these promising properties, important work has also been taking place on MNPs in combination with proteins. MNPs can be used to improve the in vivo properties of therapeutic proteins, increasing their circulation half-lives. On the other hand, proteins are very important candidates to improve the in vivo fate of MNPs, as they can be used for their site-specific active targeting, as well as the enhancement of their colloidal stability in physiological conditions. In this review, we describe the most common preparation methods of protein modified MNPs used for biomedical applications and highlight the most promising ones for each purpose.