Sinteza in vrednotenje encimskega zaviranja vinilnih in jodopiridinskih zaviralcev MurA

Kraljič, Karmen (author), Hrast, Martina (mentor)

Odkritje antibiotikov in začetek njihove množične uporabe v 40. letih prejšnjega stoletja je eden največjih mejnikov v zgodovini medicine. Njihova široka uporaba ni le zmanjšala smrtnosti zaradi infekcijskih bolezni, ampak je pripomogla tudi k razvoju bakterijskih sevov, ki so odporni proti posameznim ali celo več različnim protibakterijskim učinkovinam. Potreba po novih protibakterijskih zdravilih z novim mehanizmom delovanja, ki bi zaobšel odpornost, je večja kot kadarkoli prej. Ena najbolj raziskanih in validiranih tarč za protibakterijsko terapijo je biosinteza peptidoglikana, saj poškodba bakterijske celične stene ali zaviranje sinteze peptidoglikana vodi v celično lizo. Ker človeške celice nimajo celične stene, so taka zdravila selektivno toksična za bakterije. Encim MurA ligaza je zelo obetavna tarča za odkrivanje novih protibakterijskih učinkovin, saj katalizira ključen korak v biosintezi peptidoglikana, ni prisoten v organizmih sesalcev in nima homologa med človeškimi proteini. Poleg tega je validirana tarča, saj ga zavira protibakterijsko zdravilo fosfomicin, ki je v klinični uporabi. V okviru magistrske naloge smo sintetizirali nove možne zaviralce encima MurA, pri čemer smo izhajali iz monosubstituiranih vinilpiridinov in jodopiridinov, znanih zaviralcev encima MurA. S pomočjo enostopenjskih reakcij smo sintetizirali 15 disubstiutiranih vinil- in jodopiridinov iz komercialno dostopnih disubstituiranih bromopiridinov, pri čemer smo brom zamenjali z vinilno skupino ali z jodom. Z biokemijskim testiranjem smo preverili zaviralno delovanje novo sintetiziranih spojin na MurA iz E.coli. Za najbolj učinkovite so se izkazale spojine 2, 3, 5a in 6, vsi vinilpiridini, za katere je bila pri koncentraciji 500 µM rezidualna aktivnost encima manjša od 50 %. Spojini 2 in 3, ki sta najbolj zavirali encim MurA imata obe metilno skupino na orto poziciji in vinilno skupino na meta poziciji glede na piridinski dušik, kar se je med našimi spojinami izkazalo za najbolj obetavno kombinacijo substituentov. Vrednosti IC50 so za spojine 2, 3, 5a in 6 v mikromolarnem območju, vendar jih ocenjujemo kot dobre, saj so naše spojine mišljene le kot fragmenti zaviralcev MurA. Na podlagi rezultatov lahko iz fragmentov 2, 3, 5a in 6 naprej razvijamo močnejše, selektivne zaviralce MurA.

• Language: Slovenian
• Keywords: encim MurA, protibakterijske učinkovine, peptidoglikan, vinilpiridin, jodopiridin
• Work type: Master's thesis/paper
• Organization: FFA - Faculty of Pharmacy
• Year: 2020
• PID: 20.500.12556/RUL-120349
• Publication date in RUL: 18.09.2020

Secondary language

• Language: English
• Title: Synthesis and evaluation of vinyl and iodopyridine MurA inhibitors

Abstract

The discovery of antibiotics in 1940s and their subsequent widespread use is one of the greatest achievements of modern medicine. Although their broad use lowered mortality due to infectious disease, it also contributed to development of resistant and multidrug resistant bacteria. The need for new antibacterial agents with novel mechanisms to circumvent the resistance is greater than ever before. Peptidoglycan biosynthesis is one of the most promising and validated targets for novel antibacterials as damaging bacterial cell wall or inhibiting its synthesis lead to cell lysis. Human cells do not have any peptidoglycan; therefore, such antibacterial drugs are selectively toxic to bacteria. The enzyme MurA ligase catalyzes a crucial step of peptidoglycan biosynthesis, is not present in mammals and shows poor homology with human proteins, hence it is a very promising target for novel drug discovery. It is also a validated target, as it is inhibited by an antibiotic in clinical use, called fosfomycin. In this master's thesis we synthesized new potential MurA inhibitors based on known monosubstituted vinyl- and iodopyridine scaffolds. A new series of 15 disubstituted vinyl- and iodopyridines was synthesized from commercially available disubstituted bromopyridines. In one-step synthesis we exchanged the bromine atom with the vinyl group or with an iodine atom. Synthesized compounds were tested for their inhibitory activity on MurA from E. coli. Vinyl compounds 2, 3, 5a and 6 were most potent with the residual activity of MurA less than 50 % at 500 µM. Compounds 2 and 3 both having a methyl group in ortho and a vinyl group in meta position were identified as most potent and most suitable for further modification. IC50 values for compounds 2, 3, 5a and 6 were in the micromolar range. Considering our compounds are meant to function as fragments of a larger molecule the results are very promising. To conclude, based on fragments 2, 3, 5a and 6 it may be possible to develop new inhibitors of MurA with high specificity and potency.

• Keywords: MurA enzyme, antibacterial agents, peptidoglycan, vinylpyridine, iodopyridine