Discovery and structural characterization of a thermostable bacterial monoamine oxidase.

Monoamine oxidases (MAOs) are pivotal regulators of neurotransmitters in mammals, while microbial MAOs have been shown to be valuable biocatalysts for enantioselective synthesis of pharmaceutical compounds or precursors thereof. To extend the knowledge of how MAOs function at the molecular level and in order to provide more biocatalytic tools, we set out to identify and study a robust bacterial variant: a MAO from the thermophile Thermoanaerobacterales bacterium (MAOTb ). MAOTb is highly thermostable with melting temperatures above 73 °C and is well expressed in Escherichia coli. Substrate screening revealed that the oxidase is most efficient with n-alkylamines with n-heptylamine being the best substrate. Presteady-state kinetic analysis shows that reduced MAOTb rapidly reacts with molecular oxygen, confirming that it is a bona fide oxidase. The crystal structure of MAOTb was resolved at 1.5 Å and showed an exceptionally high similarity with the two human MAOs, MAO A and MAO B. The active site of MAOTb resembles mostly the architecture of human MAO A, including the cysteinyl protein-FAD linkage. Yet, the bacterial MAO lacks a C-terminal extension found in human MAOs, which explains why it is expressed and purified as a soluble protein, while the mammalian counterparts are anchored to the membrane through an α-helix. MAOTb also displays a slightly different active site access tunnel, which may explain the specificity toward long aliphatic amines. Being an easy-to-express, thermostable enzyme, for which a high-resolution structure was elucidated, this bacterial MAO may develop into a valuable biocatalyst for synthetic chemistry or biosensing.

Targeting ROS production through inhibition of NADPH oxidases.

NADPH oxidases (NOXs) are transmembrane enzymes that are devoted to the production of reactive oxygen species (ROS). In cancers, dysregulation of NOX enzymes affects ROS production, leading to redox unbalance and tumor progression. Consequently, NOXs are a drug target for cancer therapeutics, although current therapies have off-target effects: there is a need for isoenzyme-selective inhibitors. Here, we describe fully validated human NOX inhibitors, obtained from an in silico screen, targeting the active site of Cylindrospermum stagnale NOX5 (csNOX5). The hits are validated by in vitro and in cellulo enzymatic and binding assays, and their binding modes to the dehydrogenase domain of csNOX5 studied via high-resolution crystal structures. A high-throughput screen in a panel of cancer cells shows activity in selected cancer cell lines and synergistic effects with KRAS modulators. Our work lays the foundation for the development of inhibitor-based methods for controlling the tightly regulated and highly localized ROS sources.

Ciprofloxacina vs cefotaxima en infecciones de piel y tejidos blandos / Ciprofloxacin vs cifotaxine in skin and bland tissues infections

Se realizó un estudio clínico abierto, prospectivo, comparativo y aleatorio en el cual se evaluó la seguridad y efectividad de la ciprofloxacina por vía oral (500 mg/12 horas) vs cefotaxima por vía parenteral (1 gr/8 horas) en el tratamiento de infecciones de piel y tejidos blandos. Del total de 60 pacientes incluidos en el estudio, 47 fueron evaluables, 25 pacientes en el grupo de ciprofloxacina y 22 en el grupo de cefotaxina. Ambos grupos fueron comparables en cuanto a sus características clínicas. En los dos grupo predominaron los microorganismos gram positivos, siendo el Staphylociccus aureus la cepa aislada con mayor frecuencia. Se obtuvo la curación en 23 pacientes (92%) y 22 pacientes (100%) en el grupo de ciprofloxamina y cefotaxima, respectivamente. Se apreció mejoría clínica en 2 pacientes con ciprofloxacina (8%). La erradicación bacteriológica se observó en el 92% en el grupo que recibió ciprofloxacina y en el 86,9% en el grupo que recibió cefotaxima. No hubo efectos colaterales importantes en nigún paciente. La ciprofloxacina es equivalente a la cefotaxima, en cuanto a su efectividad y tolerabilidad en este tipo de infecciones