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Brazilian Medicinal Plant Extracts with Antimicrobial Action Against Microorganisms that Cause Foodborne Diseases
Published in Mahendra Rai, Chistiane M. Feitosa, Eco-Friendly Biobased Products Used in Microbial Diseases, 2022
Luiza Helena da Silva Martins, Sabrina Baleixo da Silva, Carissa Michelle Goltara Bichara, Johnnat Rocha Allan de Oliveira, Adilson Ferreira Santos Filho, Rafaela Cristina Barata Alves, Andrea Komesu, Mahendra Rai
Studies have shown the significant action of flavonoids as topoisomerase inhibitors, contributing to their antimicrobial activity. According to Plaper et al. (2003), DNA gyrase is defined as an essential enzyme so that DNA replication can be performed, being exclusive to prokaryotes, and an attractive target for drugs with antimicrobial action. Quercetin, apigenin and sakuranet are flavonoids capable of inhibiting Helicobacter pylori 3-hydroxyacyl ACP dehydrase (Zhang et al. 2008). Eleven flavanones with different configurations of hydroxyl groups were evaluated to verify the antimicrobial activity on E. faecalis (Jeong et al. 2009) and many were shown to be efficient, mainly being naringenin and taxifolin. Mori et al. (1987) reported that some flavonoids can affect the DNA of microorganisms, and act in the inhibition of bacterial nucleic acid synthesis. They noted that the incubation with epigallocatechin gallate, myricetin and robinetin resulted in the reduction of DNA, RNA and protein synthesis by Proteus vulgaris and S. aureus.
Role of Plant-Based Bioflavonoids in Combating Tuberculosis
Published in Megh R. Goyal, Durgesh Nandini Chauhan, Assessment of Medicinal Plants for Human Health, 2020
Alka Pawar, Yatendra Kumar Satija
Fluoroquinolones were discovered in the year 1965 as a derivative in the purification of the Chloroquine—an antimalarial drug. It mainly inhibits the type II topoisomerase/DNA gyrase enzyme of MTB. The DNA gyrase consists of subunits A and B, coded via gyr genes. Resistance of fluoroquinolones mainly occurs due to mutation in gyrA or gyrB genes.78
Urolithiasis
Published in Manit Arya, Taimur T. Shah, Jas S. Kalsi, Herman S. Fernando, Iqbal S. Shergill, Asif Muneer, Hashim U. Ahmed, MCQs for the FRCS(Urol) and Postgraduate Urology Examinations, 2020
Thomas Johnston, James Armitage, Oliver Wiseman
Beta (β)-lactam antibiotics contain a β-lactam ring in their molecular structure, which act as an irreversible inhibitor of the enzyme transpeptidase, which is used by the bacteria to cross-link peptidoglycan in their cell walls. β-lactam antibiotics include penicillin derivatives (penams such as amoxicillin), cephalosporins (cephems such as cephalexin) and carbapenems (such as meropenem or itrapenem). Aminoglycosides (gentamicin) are important treatments against Gram-negative infections. They act by inhibiting protein synthesis by binding to ribosomal RNA, which disrupts the integrity of the bacterial cell wall membrane. Sulphonamides are one of the oldest groups of antibiotic compounds (trimethoprim-sulphonamide) in use. They are structurally similar to para-aminobenzoic acid (PABA) and act as a false substrate for the enzyme dihydrofolate synthase, which blocks the synthesis of folate. This results in inhibition of DNA synthesis and therefore bacterial cell growth. Fluoroquinolone (ciprofloxacin) antibiotics inhibit the enzyme DNA gyrase, which is essential for transcription bacterial DNA synthesis, and results in irreversible damage and bacterial cell death. Nitrofurantoin is reduced inside the bacterial cell by flavoproteins (nitrofuran reductase) to multiple intermediates that attack ribosomal proteins (ribosomal subunit 50 S and target 23 S ribosomal RNA, DNA and pyruvate metabolism (Table 16.2).
Bacterial death from treatment with fluoroquinolones and other lethal stressors
Published in Expert Review of Anti-infective Therapy, 2021
Many bacterial species contain two type-II DNA topoisomerases, DNA gyrase and DNA topoisomerase IV (some, such as Mycobacterium tuberculosis, contain only gyrase). These enzymes alter DNA topology by introducing a double-strand break, passing another duplex (or a another region of the same duplex) through the break, and then resealing the break. The quinolones form complexes with either gyrase or topoisomerase IV and DNA that is broken such that each 5ʹ end is covalently bound to either GyrA (gyrase) or ParC (topoisomerase IV) [15,16]. Since the DNA is broken, the complex is called a cleaved complex (Figure 3). The presence of a covalent protein-DNA link allows the DNA break to readily reseal when quinolone is removed. As expected, cleaved-complex formation in vitro is reversible [17,18].
Genetic functional algorithm model, docking studies and in silico design of novel proposed compounds against Mycobacterium tuberculosis
Published in Egyptian Journal of Basic and Applied Sciences, 2020
A type II topoisomerase target ‘DNA gyrase’ is a present in all bacteria. It produces negative supercoils for the whole bacterial chromosome which relaxes the supercoils that generates the translocating RNA polymerase which shortened the chromosome for appropriate segregating during cell division [4,5]. This enzyme is a tetramer that made up of ‘two subunits A,’ which comprises of the DNA binding domain and ‘two subunits B’ which catalyzes the reaction that quickly cleaves two DNA strands which depend on ATP hydrolysis. The two subunit A and B i.e. GyrA and GyrB aids the DNA replication by breaking and reuniting the DNA strand. Based on the function stated, the termination of the DNA replication can be blocked by prominent inhibitors either targeting the GyrA (DNA domain) or GyrB (ATP binding cavities).
DNA topoisomerases as molecular targets for anticancer drugs
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Kamila Buzun, Anna Bielawska, Krzysztof Bielawski, Agnieszka Gornowicz
Type IIA topoisomerases subfamily includes eukaryotic Top II, bacterial DNA gyrase, human topoisomerase II and bacterial Top IV39. The sequences of all the enzymes belonging to the family of type IIA topoisomerases (Top IIA) show significant similarity, and the only differences are found in the quaternary structures of these proteins. Gyrase and topoisomerase IV (Top IV) belonging to type IIA bacterial topoisomerases are composed of two subunits: the ParE and ParC which are homologues of the GyrB and GyrA subunits of gyrase. In terms of structure, prokaryotic type IIA topoisomerases are referred to as heterotetramers in contrast to eukaryotic enzymes which belong to the group of homodimers. The N-terminal half-ends of the eukaryotic Top IIA are homologues of the GyrB/ParE subunits of gyrase and Top IV, and the central parts of the enzymes are homologues of the GyrA/ParC subunits (gyrase/Top IV). The C-terminal half-ends, unlike the N-terminal parts of the eukaryotic topoisomerases type IIA, show significant structural differences between the enzymes of different eukaryotes. Analysis of C-terminal eukaryotic and prokaryotic type IIA topoisomerases did not show similarities in the sequence of these enzymes40.