Structural characterization of cassava linamarase-linamarin enzyme complex: an integrated computational approach.

Cassava linamarase is a hydrolyzing enzyme that belongs to a glycoside hydrolase family 1 (GH1). It is responsible for breaking down linamarin to toxic cyanide. The enzyme provides a defensive mechanism for plants against herbivores and has various applications in many fields. Understanding the structure of linamarase at the molecular level is a key to avail its reaction mechanism. In this study, the three-dimensional (3D) structure of linamarase was built for the first time using homology modelling and used to study its interaction with linamarin. Molecular docking calculations established the binding and orientation nature of linamarin, while molecular dynamics (MD) simulation established protein-ligand complexes' stability. Binding-free energy based on MM/PBSA was further used to rescore the docking results. An ensemble structure was found to be relatively stable compared to the modelled structure. This study sheds light on the exploration of linamarase towards understanding its reaction mechanisms.Communicated by Ramaswamy H. Sarma.

Drug development against sleeping sickness: old wine in new bottles?

Atoxyl, the first medicinal drug against human African trypanosomiasis (HAT), also known as sleeping sickness, was applied more than 100 years ago. Ever since, the search for more effective, more specific and less toxic drugs continued, leading to a set of compounds currently in use against this devastating disease. Unfortunately, none of these medicines fulfill modern pharmaceutical requirements and may be considered as therapeutic ultima ratio due to the many, often severe side effects. Starting with a historic overview on drug development against HAT, we present a selection of trypanosome specific pathways and enzymes considered as highly potent druggable targets. In addition, we describe cellular mechanisms the parasite uses for differentiation and cell density regulation and present our considerations how interference with these steps, elementary for life cycle progression and infection, may lead to new aspects of drug development. Finally we refer to our recent work about CNS infection that offers novel insights in how trypanosomes hide in an immune privileged area to establish a chronic state of the disease, thereby considering new ways for drug application. Depressingly, HAT specific drug development has failed over the last 30 years to produce better suited medicine. However, unraveling of parasite-specific pathways and cellular behavior together with the ability to produce high resolution structures of essential parasite proteins by X-ray crystallography, leads us to the optimistic view that development of an ultimate drug to eradicate sleeping sickness from the globe might just be around the corner.