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Title: Identification and Study of Mechanism of Action of Inhibitors of Urease's of Diverse Origins
Authors: Khan, Majid
Keywords: Physical Sciences
Issue Date: 2021
Publisher: University of Karachi, Karachi
Abstract: Several unique features make enzymes useful drug targets. Each enzyme catalyzes only a single type of biochemical reaction, and repeatedly produce the desired product efficiently. Current pharmacopeia comprises of almost half of the clinically used drugs that act as enzyme inhibitors. Part A In the first phase of study, more than 3,500 fully characterized chemical compounds and 600 drugs were investigated for their inhibitory potential against Jack bean urease enzyme. Acetohydroxamic acid (FDA approved Urease inhibitor) was used as the standard inhibitor (IC50 = 20.34 ± 0.43 µM). As a result of medium throughput screening, 97 compounds of various classes and some drugs were identified as potent inhibitors of urease enzyme. Among them compounds 1, 14, 39, 63, 91, 126, 136, and 140 showed potent activities with IC50 value in the range of 5.82 - 12.31 µM. Mechanistic studies were then carried out to determine their modes of inhibition and dissociation constant (Ki) via Lineweaver-Burk and Dixon Graphs. Kinetic studies revealed that most of these compounds inhibit enzyme in competitive manner, while some of them act as non-competitive or mixed inhibitors. Some of the active compounds (2, 3, 5, 6, 8-10, 14, 15, and 31) were also evaluated against the bacterial (Proteus mirabilis) urease. These compounds inhibit bacterial urease with the same potency as that of plant urease, which further validates that plant urease can be used as an excellent model for primary screening of urease inhibitors. Cell cytotoxicity studies were employed in last on all compounds against (3T3) mouse fibroblast cell line. Most of the active compounds were found non-cytotoxic. Part B Second part of this dissertation focuses on the computational studies on ureases from Proteus mirabilis and Jack bean (Canavalia ensiformis (Linn.)). Using Homology modeling tools, the 3D model of Proteus mirabilis urease was constructed for the first time using Jack bean urease enzyme as template (PDB: 4GY7). After that, selective compounds i.e., 1, 2, 3, 11 and 12 were docked against modeled and Jack bean ureases. The docking studies revealed that all inhibitors showed a similar type of interactions with the active site residues of both ureases. This indicates that the predicted 3D model can be used for virtual screening of urease inhibitors.
Gov't Doc #: 27003
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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