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    Application of reductive amination by heterologously expressed Thermomicrobium roseum L-alanine dehydrogenase to synthesize L-alanine derivatives
    (Elsevier Science Inc, 2023) Dedeakayogullari, Huri; Valjakka, Jarkko; Turunen, Ossi; Yilmazer, Berin; Demir, Garip; Janis, Janne; Binay, Baris
    Unnatural amino acids are unique building blocks in modern medicinal chemistry as they contain an amino and a carboxylic acid functional group, and a variable side chain. Synthesis of pure unnatural amino acids can be made through chemical modification of natural amino acids or by employing enzymes that can lead to novel molecules used in the manufacture of various pharmaceuticals. The NAD+ -dependent alanine dehydrogenase (AlaDH) enzyme catalyzes the conversion of pyruvate to L-alanine by transferring ammonium in a reversible reductive amination activity. Although AlaDH enzymes have been widely studied in terms of oxidative deamination activity, reductive amination activity studies have been limited to the use of pyruvate as a substrate. The reductive amination potential of heterologously expressed, highly pure Thermomicrobium roseum alanine dehydrogenase (TrAlaDH) was examined with regard to pyruvate, a-ketobutyrate, a-ketovalerate and a-ketocaproate. The biochemical properties were studied, which included the effects of 11 metal ions on enzymatic activity for both reactions. The enzyme accepted both derivatives of L-alanine (in oxidative deamination) and pyruvate (in reductive amination) as substrates. While the kinetic KM values associated with the pyruvate derivatives were similar to pyruvate values, the kinetic k(cat) values were significantly affected by the side chain increase. In contrast, K-M values associated with the derivatives of L-alanine (L-a-aminobutyrate, L-norvaline, and L-norleucine) were approximately two orders of magnitude greater, which would indicate that they bind very poorly in a reactive way to the active site. The modeled enzyme structure revealed differences in the molecular orientation between L-alanine/pyruvate and L-norleucine/a-ketocaproate. The reductive activity observed would indicate that TrAlaDH has potential for the synthesis of pharmaceutically relevant amino acids.
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    Beneficial effects of adipose-derived stromal vascular fraction on testicular injury caused by busulfan
    (Taylor & Francis Ltd, 2024) Hekimoglu, E. Rumeysa; Esrefoglu, Mukaddes; Karakaya Cimen, Fatma Bedia; Elibol, Birsen; Dedeakayogullari, Huri; Pasin, Ozge
    The use of stem cells can attenuate testicular injury and promote sperm production. The adipose-derived stromal vascular fraction (SVF) has become an attractive cell source for cell-based therapies. In this study, we aimed to investigate the therapeutic efficacy of SVF on busulfan-induced testicular damage in rats. Twenty-four male rats were randomly divided into control, busulfan, SVF, and busulfan + SVF groups. Testicular damage was induced by intraperitoneal administration of busulfan (35 mg/kg). SVF obtained from human adipose tissue using Lipocube SVF (TM) was injected into rats 5 weeks after busulfan administration. At the end of the 8th week, rats were sacrificed, and histopathological, biochemical, and western blotting analyses were performed. No harmful effects of SVF on healthy testis tissue and sperm parameters were detected. SVF improved busulfan-induced oxidative stress in both testis tissue and serum. SVF injection to damaged testicular tissue resulted in increases in the healthy spermatozoon numbers and decreases in the abnormal tail numbers. Additionally, SVF increased bax/Bcl, DAZL, and TGF-beta 1 levels whereas decreased ATG5 and NF-kB levels. According to the results we obtained in this study, we suggest that SVF is beneficial in restoring damaged tissue by primarily being a multipotent cell source, by inhibiting oxidative stress and converting necrotic cell death to apoptotic cell death. In the future, clinical applications should bring higher benefits. Since SVF is the patient's own tissue, being harmless, it will offer an advantageous supportive treatment option for patients already weakened by cancer and anticancer therapy.