Project description:Glutaminase (GLS) is an enzyme essential for amino acid metabolism; in particular, it acts as a catalyst in glutaminolysis, a reaction exploited by the malignant cells to meet the nutrient requirements for their accelerated growth and proliferation. Via regulating the initial reaction of the glutaminolysis pathway, glutaminase offers an intriguing target for the development of anticancer drugs. In the present study, we produced a recombinant glutaminase from Geobacillus thermodenitrificans DSM-465 in E. coli. The enzyme was purified to electrophoretic homogeneity, with 40% recovery and 22.36 fold purity. It exhibited a molecular weight of 33 kDa, with an optimum pH and temperature of 9 and 70 °C, respectively. The K M value of the purified enzyme was 104 μM for l-glutamine. A 3D model was built for the enzyme using Swiss-Model and subjected to molecular docking with the substrate and potential inhibitors. Moreover, the subject enzyme was compared with the human kidney type GLS-K by ConSurf and TM-align servers for evolutionary conserved residues and structural domains. Despite having less than 40% amino acid identity, the superimposed monomers of both enzymes exhibited ∼94% structural identity. With a positional difference, the active site residues Ser65, Asn117, Glu162, Asn169, Tyr193, Tyr245, and Val263 found in the bacterial enzyme were also conserved in the human GLS-K. Molecular docking results have shown that CB-839 is the best inhibitor for GLS-GT and UPGL00004 is the best inhibitor for GLS-K, as designated by the binding free energy changes, i.e. ΔG -388.7 kJ mol-1 and ΔG -375 kJ mol-1, respectively. Moreover, six potential inhibitory molecules were ranked according to their binding free energy change values for both enzymes. The information can be used for the in vivo anticancer studies.
Project description:The present work aimed at discovering xylose-inducible and glucose-insensitive promoters from Geobacillus thermoglucosidasius DSM 2542. This strategy enabled the pathway from xylose metabolism to riboflavin production activated by xylose but not glucose, so that glucose was mainly used for cell growth while xylose was used for riboflavin production. By performing whole genome transcriptional analysis of G. thermoglucosidasius DSM 2542 with or without 1% xylose, 71 xylose-activated genes were identified which were controlled by 39 putative promoters. 3 experimentally validated xylose-inducible and glucose-insensitive promoters covering a broad range of transcriptional levels were used to activate the extra pathway from xylose metabolism to riboflavin production. Fermentation results showed the good performance of these promoters for riboflavin production improvement comparing to constitutive promoters. Therefore, our strategy could be applicable to the construction of cell factories that can efficiently use natural carbon sources with glucose and xylose components for the production of high-value chemicals.