scholarly journals Computer-aided engineering of a branching sucrase for the glucodiversification of a tetrasaccharide precursor of S. flexneri antigenic oligosaccharides

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mounir Benkoulouche ◽  
Akli Ben Imeddourene ◽  
Louis-Antoine Barel ◽  
Dorian Lefebvre ◽  
Mathieu Fanuel ◽  
...  

AbstractEnzyme engineering approaches have allowed to extend the collection of enzymatic tools available for synthetic purposes. However, controlling the regioselectivity of the reaction remains challenging, in particular when dealing with carbohydrates bearing numerous reactive hydroxyl groups as substrates. Here, we used a computer-aided design framework to engineer the active site of a sucrose-active $$\mathrm{\alpha }$$ α -transglucosylase for the 1,2-cis-glucosylation of a lightly protected chemically synthesized tetrasaccharide, a common precursor for the synthesis of serotype-specific S. flexneri O-antigen fragments. By targeting 27 amino acid positions of the acceptor binding subsites of a GH70 branching sucrase, we used a RosettaDesign-based approach to propose 49 mutants containing up to 15 mutations scattered over the active site. Upon experimental evaluation, these mutants were found to produce up to six distinct pentasaccharides, whereas only two were synthesized by the parental enzyme. Interestingly, we showed that by introducing specific mutations in the active site of a same enzyme scaffold, it is possible to control the regiospecificity of the 1,2-cis glucosylation of the tetrasaccharide acceptor and produce a unique diversity of pentasaccharide bricks. This work offers novel opportunities for the development of highly convergent chemo-enzymatic routes toward S. flexneri haptens.

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Muhammad Tukur Ibrahim ◽  
Adamu Uzairu ◽  
Gideon Adamu Shallangwa ◽  
Sani Uba

Abstract Background The treatment of epidermal growth factor receptor (EGFR)-muted non-small cell lung cancer (NSCLC) remains among the utmost important unachieved therapeutic need worldwide. Development of EGFR inhibitors to treat NSCLC mutations has been among the difficult tasks faced by researchers in this area. As such, there is a need to discover more EGFR inhibitors. The purpose of this work is to perform computer-aided/structure-based design of novel EGFR inhibitors, elucidate their nature of interactions with their target, and also assess their ADMET properties as well as their drug-likeness, respectively. Compound 17 with a highest binding affinity of −9.5kcal/mol was identified as the template hit compound using molecular docking virtual screening in our previous work. The compound interacted with the active site of the EGFR receptor via hydrogen bond with the following amino acid residues MET793, MET793, THR854, and ASP855 with bond distances of 2.61394 (Å), 2.18464 (Å), 2.57601 (Å), and 2.68794 (Å), respectively. It also interacted with the active site of the EGFR receptor via halogen bond (GLN791), hydrophobic bond (LEU718, CYS797, LYS745, ALA743, ALA743, and VAL726), electrostatic bond (LYS745), and others (MET766), respectively. Furthermore, from our previous study, the following descriptors (ATSC6m, ATSC8e, MATS7m, SpMax3_Bhp, SpMax5_Bhs, and MaxHBint10) contained in the reported model were found to be responsible for the inhibitory activities of the studied compounds. In this research, the template (compound 17) was modified manually by attaching halo-phenyl and halo-phenyl-amino rings on the para position of the flouro-nitro-benzamide moiety of the template compound, respectively. Results A computer-aided design/structure-based approach was used to design six new EGFR inhibitors using molecule 17 as the template compound for the design identified in our previously reported work. Molecular docking investigation was performed to elucidate the binding mode of these newly designed EGFR inhibitors with the binding pose of EGFR receptor (pdb code 4ZAU) and found to have better affinities which range from −9.5 to −10.4 kcal/mol than the template compound and gefitinib, the control, respectively. The ADMET property assessment of these newly designed EGFR inhibitors indicated that they were orally bioavailable with good absorption, distribution, metabolism, and excretory properties with no toxicity. And for their drug-likeness, they were seen to have a higher molecular weight which might be as a result of halo-phenyl-amino ring attachments. Based on this finding, halo-phenyl-amino rings might be responsible for the inhibitory activities of these newly designed compounds. Conclusion The six newly designed EGFR inhibitors were found to have higher binding affinities toward their target EGFR receptor than the template compound and gefitinib which was used as the control in this research. They were seen to have good ADMET and drug-like properties which indicate that they might be orally bioavailable. Furthermore, according to their synthetic accessibility score, they can be easily synthesized in the laboratory because the values were found to be less than five which fall within the easy portion of the scale. Therefore, this research recommends that these newly designed EGFR inhibitors should be synthesized most especially those with higher binding affinities, good ADMET, and drug-likeness properties than the template compound.


2011 ◽  
Vol 12 (4) ◽  
Author(s):  
Ibrahim Ali Noorbatcha ◽  
Nur Izzah Ismail ◽  
And Hamzah Mohd. Salleh

Pectin is a complex polysaccharide found in the cell walls of plants and consisting mainly of esterified D-galacturonic acid resides in α-(1-4) chain. In production of fruit juice, pectin contributes to fruit juice viscosity, thereby reducing the juice production and increasing the filtration time. Polygalacturonase improves the juice production process by rapid degradation of pectin. In this project we have designed a novel polygalacturonase enzyme using computer aided design approaches. The three dimension structure of polygalacturonase is first modeled on the basis of the known crystal structure. The active site in this enzyme is identified by manual and automated docking methods. Lamarckian genetic algorithm is used for automated docking and the active site is validated by comparing with existing experimental data. This is followed by in silico mutations of the enzymes and the automated docking process is repeated using the mutant enzymes. The strength of the binding of the ligands inside the active site is evaluated by computing the binding score using Potential Mean Force (PMF) method. The in silico mutations R256Q and K258N are found to decrease the binding strength of the ligand at the active site, indicating lowering of enzyme activity, which is consistent with the experimental results. Hence in silico mutations can be used to design new polygalacturonase enzymes with improved enzyme activity.ABSTRAK: Pektin adalah polisakarida kompleks yang terdapat di dalam dinding sel tumbuhan dan sebahagian besarnya terdiri daripada asid D-galakturonik terester yang ditemui di dalam rantaian α-(1-4). Dalam penghasilan jus buah-buahan, pektin menyumbang dalam kepekatan jus buah-buahan, di mana ia mengurangkan penghasilan jus dan menambahkan masa penapisan. Poligalakturonase meningkatkan proses penghasilan jus dengan pemecahan pektin dengan cepat. Dalam projek ini, kami telah merangka satu enzim poligalakturonase baru dengan menggunakan pendekatan reka bentuk berbantukan komputer. Struktur tiga dimensi poligalakturonase ini pada permulaannya dimodelkan berasaskan kepada struktur kristal. Tapak aktif enzim ini dikenali pasti dengan kaedah mengedok manual dan automatik. Algoritma genetik Lamarckian digunakan untuk dok berautomatik dan tapak aktif ini disahkan dengan perbandingan dengan data eksperimental yang sedia ada. Kaedah ini diikuti pula dengan mutasi in siliko enzim dan proses mengedok automatik diulangi dengan menggunakan enzim mutan. Kekuatan ikatan ligan yang berada di dalam tapak aktif dinilai dengan mengira kiraan ikatan menggunakan kaedah Min Keupayaan Daya (Potential Mean Force (PMF)). Mutasi in siliko R256Q dan K258N merupakan penyebabpenurunan dalam kekuatan ikatan ligan di tapak aktif, menunjukkan pengurangan dalam aktiviti enzim, di mana ianya konsisten dengan keputusan ekperimental. Jesteru, mutasi siliko boleh digunakan untuk mereka enzim poligalakturonase baru dengan mempertingkatkan aktiviti enzim.


2018 ◽  
Vol Volume 12 ◽  
pp. 1239-1254 ◽  
Author(s):  
Tayebeh Farhadi ◽  
Seyed MohammadReza Hashemian

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