Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Rational Design of Hemoproteins for Peroxidation Reactions(01. Izmir Institute of Technology, 2020) Güralp, Gülce; Güralp, Gülce; Sürmeli Eraltuğ, Nur Başak; 01. Izmir Institute of TechnologyBiocatalysts are important for the synthesis of fine chemicals and steroidal drugs in the biopharmaceutical industry. Cytochromes P450 (P450) monooxygenases are significant biocatalysts due to their high selectivity for oxidation reactions. CYP119 is the first characterized thermoacidophilic P450. CYP119 was isolated from Sulfolobus acidocaldirius. CYP119 enzyme shows high stability at low pH and high temperature. CYP119 can utilize the peroxidase shunt pathway in the catalytic cycle of P450. These abilities make CYP119 attractive biocatalyst for production of fine chemicals and drugs. In this study, Leu69Gly mutant CYP119 enzyme was cloned by site-directed mutagenesis. L69G and WT CYP119 was expressed successfully in Escherichia coli BL21 (DE3) cells with isopropyl β-D-1- thiogalactopyranoside (IPTG). This study shows that L69G mutation is important for binding to progesterone. This was predicted by in silico mutagenesis in a previous computational study. Isolation and purification of the WT and L69G CYP119 were carried out. Activity assays and substrate binding studies of the enzymes were performed and compared each other. L69G mutation did not cause significant effect on Amplex Red® oxidation and styrene epoxidation activities. L69G CYP119 (KS: 34.55 ± 7.4 μM) showed higher affinity for progesterone compared to WT CYP119 (KS: 69.8 ± 48.9 mM). A new product, thought to be hydroxylated progesterone, was formed as result of hydroxylation of progesterone by L69G CYP119 using peroxidase shunt pathway.Master Thesis Chemical Characterization of Caldanaerobacter Subterraneus Subsp. Tengcongensis Heme-Nitric Oxide/Oxygen Binding Protein(01. Izmir Institute of Technology, 2020) Sürmeli, Nur Başak; Sürmeli, Nur Başak; Sürmeli, Nur Başak; 03.01. Department of Bioengineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyHemoproteins, which contain the heme prosthetic group , take part in different biological processes in many stages of life. Their ability to catalyze important biosynthesis reactions makes them good candidates for understanding and elucidating complex mechanisms for biocatalysis. In this study, the catalytic properties of thermophilic Thermoanaerobacter tencogensis nitric oxide/oxygen binding protein, a heme protein reshaped by rational design, were investigated and chemical characterization was carried out. The peroxidase activity of the enzyme was investigated by the oxidation reactions of guaiacol, amplex red and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS). Kinetic parameters of the reactions were determined. These obtained results demonstrated that, in the presence of H2O2, wild type and Y140H TtH-NOX proteins are able to catalyze oxidation reactions of guaiacol, Amplex red and ABTS. Comparison of the kinetic parameters showed that Y140H mutant catalyzed the guaiacol and ABTS oxidation 3-fold and 15 -fold faster than wild type enzyme, respectively. The stability of TtH-NOX proteins were investigated in the presence of organic solvents. Results were demonstrated that WT TtH-NOX was more stable than Y140H mutant in the presence of organic solvents In addition to these, for the first time, thermophilic TtH-NOX proteins were immobilized with a novel enzyme immobilization method and organic-inorganic hybrid nanostrucrures were obtained. Copper ion incorporated TtH-NOX-based hybrid nanoflowers were synthesized at different pH values. SEM and EDX analysis of TtH-NOX-based hybrid nanoflowers proved that free TtH-NOXs were immobilized successfully.