Adenanthin Is an Efficient Inhibitor of Peroxiredoxins from Pathogens, Inhibits Bacterial Growth, and Potentiates Antibiotic Activities.

The emergence and re-emergence of bacterial strains resistant to multiple drugs represent a global health threat, and the search for novel biological targets is a worldwide concern. AhpC are enzymes involved in bacterial redox homeostasis by metabolizing diverse kinds of hydroperoxides. In pathogenic bacteria, AhpC are related to several functions, as some isoforms are characterized as virulence factors. However, no inhibitor has been systematically evaluated to date. Here we show that the natural ent-kaurane Adenanthin (Adn) efficiently inhibits AhpC and molecular interactions were explored by computer assisted simulations. Additionally, Adn interferes with growth and potentializes the effect of antibiotics (kanamycin and PMBN), positioning Adn as a promising compound to treat infections caused by multiresistant bacterial strains.

Functional and structural evaluation of the antileukaemic enzyme L-asparaginase II expressed at low temperature by different Escherichia coli strains.

Acute lymphoblastic leukaemia (ALL) affects lymphoblastic cells and is the most common neoplasm during childhood. Among the pharmaceuticals used in the treatment protocols for ALL, Asparaginase (ASNase) from Escherichia coli (EcAII) is an essential biodrug. Meanwhile, the use of EcAII in neoplastic treatments causes several side effects, such as immunological reactions, hepatotoxicity, neurotoxicity, depression, and coagulation abnormalities. Commercial EcAII is expressed as a recombinant protein, similar to novel enzymes from different organisms; in fact, EcAII is a tetrameric enzyme with high molecular weight (140 kDa), and its overexpression in recombinant systems often results in bacterial cell death or the production of aggregated or inactive EcAII protein, which is related to the formation of inclusion bodies. On the other hand, several commercial expression strains have been developed to overcome these expression issues, but no studies on a systematic evaluation of the E. coli strains aiming to express recombinant asparaginases have been performed to date. In this study, we evaluated eleven expression strains at a low temperature (16 °C) with different characteristics to determine which is the most appropriate for asparaginase expression; recombinant wild-type EcAII (rEcAII) was used as a prototype enzyme and the secondary structure content, oligomeric state, aggregation and specific activity of the enzymes were assessed. Structural analysis suggested that a correctly folded tetrameric rEcAII was obtained using ArcticExpress (DE3), a strain that co-express chaperonins, while all other strains produced poorly folded proteins. Additionally, the enzymatic assays showed high specific activity of proteins expressed by ArcticExpress (DE3) when compared to the other strains used in this work.

Therapeutic l-asparaginase: upstream, downstream and beyond.

l-asparaginase (l-asparagine amino hydrolase, E.C.3.5.1.1) is an enzyme clinically accepted as an antitumor agent to treat acute lymphoblastic leukemia and lymphosarcoma. It catalyzes l-asparagine (Asn) hydrolysis to l-aspartate and ammonia, and Asn effective depletion results in cytotoxicity to leukemic cells. Microbial l-asparaginase (ASNase) production has attracted considerable attention owing to its cost effectiveness and eco-friendliness. The focus of this review is to provide a thorough review on microbial ASNase production, with special emphasis to microbial producers, conditions of enzyme production, protein engineering, downstream processes, biochemical characteristics, enzyme stability, bioavailability, toxicity and allergy potential. Some issues are also highlighted that will have to be addressed to achieve better therapeutic results and less side effects of ASNase use in cancer treatment: (a) search for new sources of this enzyme to increase its availability as a drug; (b) production of new ASNases with improved pharmacodynamics, pharmacokinetics and toxicological profiles, and (c) improvement of ASNase production by recombinant microorganisms. In this regard, rational protein engineering, directed mutagenesis, metabolic flux analysis and optimization of purification protocols are expected to play a paramount role in the near future.