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Product inhibition in human manganes...

Hearn, Amy S.

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Product inhibition in human manganese superoxide dismutase.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Product inhibition in human manganese superoxide dismutase./
作者:	Hearn, Amy S.
面頁冊數:	87 p.
附註:	Chairman: David N. Silverman.
Contained By:	Dissertation Abstracts International62-10B.
標題:	Chemistry, Biochemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3027522
ISBN:	0493395245

Product inhibition in human manganese superoxide dismutase.
Hearn, Amy S.

Product inhibition in human manganese superoxide dismutase. - 87 p.

Chairman: David N. Silverman.

Thesis (Ph.D.)--University of Florida, 2001.

Human manganese superoxide dismutase (MnSOD) is a mitochondrial redox enzyme which protects the mitochondrion from oxidative damage associated with electron transport during respiration. The enzyme catalyzes the dismutation of superoxide radicals (O2<super>·</super><super>− </super>) to oxygen (O2) and hydrogen peroxide (H2O 2). The catalysis is efficient, but the enzyme becomes inhibited within the first few milliseconds of the catalysis. This inhibition is believed to result from a complex of peroxide dianion with the manganese. The active site of MnSOD is surrounded by a series of hydrophobic residues, and the goal of this work is to better understand the role of hydrophobicity in the active site and its role in inhibition. These studies focused on Trp161, a prominent hydrophobic residue which forms one wall of the active site cavity. A series of site-directed mutants of decreasing hydrophobicity were generated at position 161, and their properties were investigated using X-ray crystallography, differential scanning calorimetry, pulse radiolysis, and stopped-flow spectrophotometry.

ISBN: 0493395245Subjects--Topical Terms:

1017722
Chemistry, Biochemistry.

Product inhibition in human manganese superoxide dismutase.
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245 1 0 $a Product inhibition in human manganese superoxide dismutase.
300 $a 87 p.
500 $a Chairman: David N. Silverman.
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502 $a Thesis (Ph.D.)--University of Florida, 2001.
520 $a Human manganese superoxide dismutase (MnSOD) is a mitochondrial redox enzyme which protects the mitochondrion from oxidative damage associated with electron transport during respiration. The enzyme catalyzes the dismutation of superoxide radicals (O2<super>·</super><super>− </super>) to oxygen (O2) and hydrogen peroxide (H2O 2). The catalysis is efficient, but the enzyme becomes inhibited within the first few milliseconds of the catalysis. This inhibition is believed to result from a complex of peroxide dianion with the manganese. The active site of MnSOD is surrounded by a series of hydrophobic residues, and the goal of this work is to better understand the role of hydrophobicity in the active site and its role in inhibition. These studies focused on Trp161, a prominent hydrophobic residue which forms one wall of the active site cavity. A series of site-directed mutants of decreasing hydrophobicity were generated at position 161, and their properties were investigated using X-ray crystallography, differential scanning calorimetry, pulse radiolysis, and stopped-flow spectrophotometry.
520 $a The mutants at position Trp161 are the most inhibited enzymes reported for MnSOD, and X-ray crystallography showed that Trp161 is critical in orienting the residues involved in a hydrogen bonding network extending into the active site. This network is believed to supply the protons necessary for catalysis, and interruption of this hydrogen-bonding network may delay proton transfer and account for the increased inhibition observed in these mutants. Addition of product hydrogen peroxide to MnSOD observed by stopped-flow spectrophotometry showed that the inhibited complex can be generated by the addition of product. These experiments support the hypothesis of inhibition in the enzyme as a form of product inhibition. Solvent hydrogen isotope effects measured by pulse radiolysis were used to identify proton transfer steps in the catalysis. The decay of the inhibited complex was found to depend on proton transfer while its formation was found to have no rate-contributing proton transfer.
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