Biochemical and structural characterization of the BioZ enzyme engaged in bacterial biotin synthesis pathway

Biotin is an essential micro-nutrient across the three domains of life. The paradigm earlier step of biotin synthesis denotes “BioC-BioH” pathway in Escherichia coli. Here we report that BioZ bypasses the canonical route to begin biotin synthesis. In addition to its origin of Rhizobiales, protein phylogeny infers that BioZ is domesticated to gain an atypical role of β-ketoacyl-ACP synthase III. Genetic and biochemical characterization demonstrates that BioZ catalyzes the condensation of glutaryl-CoA (or ACP) with malonyl-ACP to give 5’-keto-pimeloyl ACP. This intermediate proceeds via type II fatty acid synthesis (FAS II) pathway, to initiate the formation of pimeloyl-ACP, a precursor of biotin synthesis. To further explore molecular basis of BioZ activity, we determine the crystal structure of Agrobacterium tumefaciens BioZ at 1.99 Å, of which the catalytic triad and the substrate-loading tunnel are functionally defined. In particular, we localize that three residues (S84, R147, and S287) at the distant bottom of the tunnel might neutralize the charge of free C-carboxyl group of the primer glutaryl-CoA. Taken together, this study provides molecular insights into the BioZ biotin synthesis pathway.

Enoyl-Acyl Carrier Protein Reductase (InhA): A REMARKABLE TARGET TO EXTERMINATE TUBERCULOSIS

: Tuberculosis, epidemic that needs new molecules with high potency and minimum side effects. In same respect, this review emphases on important target enoyl-acyl carrier protein reductase or INHA crucial in completion of FAS II cycle. INHA retain its fame since inception of drug Isoniazid as inhibitors have long residence time hence good activity. One of the cause of failure of conventional drugs is resistance towards activating or target gene. Here, we propose direct inhibitors that doesn’t need prior activation by Kat G. Some of the categories are aryl amide, Piperazine, Thiadiazole, Benzamide etc. that are specifically active against INHA along with their Structure activity relationship. Many of them are efficient in micro molar concentration whereas Pyrazole carboxamide are active in nano molar concentration and derivative of 4-hydroxy pyridones was effective in vivo. Natural products are also in way to combat tuberculosis. Furthermore, from available proteins of wild and mutant strains new leads can be designed sucessfully by utilizing information of cocrystallized ligand.

Lack of Specificity of Phenotypic Screens for Inhibitors of the Mycobacterium tuberculosis FAS-II System

ABSTRACTPhenotypic screening of inhibitors of the essential Mycobacterium tuberculosis FAS-II dehydratase HadAB led to the identification of GSK3011724A, a compound previously reported to inhibit the condensation step of FAS-II. Whole-cell-based and cell-free assays confirmed the lack of activity of GSK3011724A against the dehydratase despite evidence of cross-resistance between GSK3011724A and HadAB inhibitors. The nature of the resistance mechanisms is suggestive of alterations in the FAS-II interactome reducing access of GSK3011724A to KasA.

Metabolic Changes of Mycobacterium tuberculosis during the Anti-Tuberculosis Therapy

Tuberculosis, caused by Mycobacterium tuberculosis complex bacteria, remains one of the most pressing health problems. Despite the general trend towards reduction of the disease incidence rate, the situation remains extremely tense due to the distribution of the resistant forms. Most often, these strains emerge through the intra-host microevolution of the pathogen during treatment failure. In the present study, the focus was on three serial clinical isolates of Mycobacterium tuberculosis Beijing B0/W148 cluster from one patient with pulmonary tuberculosis, to evaluate their changes in metabolism during anti-tuberculosis therapy. Using whole genome sequencing (WGS), 9 polymorphisms were determined, which occurred in a stepwise or transient manner during treatment and were linked to the resistance (GyrA D94A; inhA t-8a) or virulence. The effect of the inhA t-8a mutation was confirmed on both proteomic and transcriptomic levels. Additionally, the amount of RpsL protein, which is a target of anti-tuberculosis drugs, was reduced. At the systemic level, profound changes in metabolism, linked to the evolution of the pathogen in the host and the effects of therapy, were documented. An overabundance of the FAS-II system proteins (HtdX, HtdY) and expression changes in the virulence factors have been observed at the RNA and protein levels.

Antiplasmodial Lycorane Alkaloid Principles of the Plant Family Amaryllidaceae

The spread of malaria is thought to have followed human expansion out of Africa some 60 – 80 thousand years ago. With its prevalence in pantropical countries of the world and epicenter localized in Africa, malaria is now considered an unnecessary burden to overworked and under-resourced healthcare structures. Plants have long afforded a fertile hunting ground for the search and identification of structurally diverse antimalarial agents, such as quinine and artemisinin. This survey examines the antiparasitic properties of the family Amaryllidaceae via the antiplasmodial activities demonstrated for its lycorane alkaloid principles. Of these, 24 were natural compounds identified in 20 species from 11 genera of the Amaryllidaceae family, whilst the remaining 28 were synthetically derived entities based on the lycorane skeleton. These were screened against ten different strains of the malarial parasite Plasmodium falciparum, wherein the parent compound lycorine was shown to be the most potent with an IC50 of 0.029 µg/mL in the FCR-3 strain seen to be the best. Structure-activity relationship studies revealed that good activities were detectable across both the natural compounds as well as the synthetically accessed derivatives. Such studies also highlighted that there are several inherent structural features that define the lycorane alkaloid antiplasmodial pharmacophore, such as the nature of its ring systems and properties of its substituents. Mechanistically, a limited number of studies confirmed that lycorane alkaloids manifest their action by targeting enzymes associated with the plasmodial FAS-II biosynthetic pathways. Overall, these alkaloids have provided useful, convenient, and accessible scaffolds for antimalarial-based drug discovery.

Induction of FAS II Metabolic Disorders to Cause Delayed Death of Toxoplasma gondii

The exact mechanism of delayed death of Toxoplasma gondii is not known. FAS II synthesis in the apicoplast of T. gondii is essential for the survival of Toxoplasma gondii, while β-hydroxyacylacyl carrier protein dehydratase (FabZ) is indispensable for fatty acid synthesis. The present study investigated the relationship between the delayed death of T. gondii by inducing metabolic disorders due to suppression the expression of FabZ. A tetracycline-induced knockout vector inserted with T. gondii fabZ gene was constructed, and transfected into T. gondii TATi strain by electroporation. The stable mutants with tetracycline-induced knockout were selected, expression of FabZ was suppressed by using anhydrotetracycline (ATc), and FAS II deficient tachyzoites were prepared. The Western blot and qPCR results revealed that proliferation of FAS II deficient tachyzoites was not significantly different compared to the normal tachyzoites at 24 h and 48 h; however, after 72 h, the number of T. gondii tachyzoites in the ATc treated group was significantly (p < 0.05) less than that of non-treated group, indicating the delayed death of T. gondii caused by the loss of apicoplast and decrease in the expression of FabZ, which inhibited the FAS II metabolism. The results of this study can be used for prevention of toxoplasmosis by inducing delayed death of T. gondii.