Interaction of mitomycin C with thiol groups of peptides and proteins.
Item
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Title
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Interaction of mitomycin C with thiol groups of peptides and proteins.
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Identifier
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AAI9325147
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identifier
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9325147
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Creator
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Sharma, Mrinalni.
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Contributor
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Adviser: Maria Tomasz
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry | Biology, Molecular
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Abstract
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Mitomycin C (MC), an antitumor antibiotic, has been widely used in clinical cancer chemotherapy. Its mode of action is intrinsically related to its ability to covalently bind DNA in both mono-functional and bifunctional manners, resulting in the latter case, in stable cross-links between the complementary strands of the genetic material.;Under physiological conditions the covalent reactivity of MC with DNA requires enzymatic or chemical reduction. In the first portion of this work, a series of different reducing agents were employed for the activation of MC (in the absence of DNA) to compare which reducing agent worked best. Reactivity of mitomycin C has been studied with a variety of thiol type nucleophiles, in order to assess whether MC could bind to peptides and proteins via their thiol groups and also whether it could be efficiently detoxified by the glutathione in the cell. Mercaptoethanol and N-acetyl cysteine, both reacted rapidly with MS, forming mono- and bis-adducts with the drug. Under physiological conditions the reactions were strictly dependent upon reductive activation of MC, by chemical reduction or various flavoreductases. Glutathione gave similar results. The structures of the adducts were determined. Surprisingly, thiol nucleophiles reacted with both alkylating functions (C-1, C-10) of MC under "monofunctional alkylating conditions". A mechanism is proposed to explain this finding.;Effects of glutathione on the crosslinking pattern of oligonucleotides and DNA with MC were also determined. H{dollar}\sb2{dollar}/PtO{dollar}\sb2{dollar}, the enzyme cytochrome c reductase and Na{dollar}\sb2{dollar}S{dollar}\sb2{dollar}O{dollar}\sb4{dollar} were used as MC activators. Extent of modification was determined by HPLC (high performance liquid chromatography) of digests. In presence of excess MC and glutathione there is decreased formation of mono- and bis-adducts of MC linked with guanines at their N{dollar}\sp2{dollar}-positions.;Extent of modification of proteins like protein kinase C and metallothionein which contain sulfhydryl groups from their cysteine residues, was also studied. In presence of MC and a reductive activator metallothionein bound MC with high affinity. Interestingly MC was also found to bind to its reductive activator, the enzyme xanthine oxidase. In addition, binding to the two proteins by the more toxic analog of NC, mitomycin A, was investigated. Results from this study indicated that mitomycin A binds to both the proteins even in the absence of reducing agents. It was not determined whether MC and MA were linked to the proteins at sulfhydryl or other alkylatable groups.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
