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Identification and characterization ...

University of Minnesota., Biochemistry, Molecular Bio, and Biophysics.

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Identification and characterization of bacterial carotenoid cleavage oxygenases.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Identification and characterization of bacterial carotenoid cleavage oxygenases./
作者:	Marasco, Erin Kathleen.
面頁冊數:	222 p.
附註:	Adviser: Claudia Schmidt-Dannert.
Contained By:	Dissertation Abstracts International69-02B.
標題:	Biology, Microbiology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoeng/servlet/advanced?query=3297480
ISBN:	9780549468097

Identification and characterization of bacterial carotenoid cleavage oxygenases.
Marasco, Erin Kathleen.

Identification and characterization of bacterial carotenoid cleavage oxygenases. - 222 p.

Adviser: Claudia Schmidt-Dannert.

Thesis (Ph.D.)--University of Minnesota, 2008.

Carotenoid cleavage oxygenases (CCOs) are non-heme iron oxygenases responsible for the oxidative cleavage of carotenoids, stilbenes and potentially other conjugated substrates. This enzyme family contains a non-canonical oxygenase active site because it is comprised of four histidines and a Fe2+. Cleavage of carotenoids by CCO enzymes has been observed in organisms from all kingdoms. The resulting cleavage products (known as apocarotenoids) have an array of biological activities (e.g. coloration, attraction of pollinators through aroma and flavors, and acting as hormones and signaling compounds). Carotenoid cleavage oxygenases were first described from metazoans and plants. Little was known about the distribution and function of CCO homologs in prokaryotes. This thesis describes the identification and functional characterization of 16 new CCO homologs from bacteria through the use of a combination of genome mining, biosynthetic pathway engineering and protein biochemistry. Findings of this thesis include the discovery of multiple active CCO paralogs in cyanobacteria; the development of methods for the isolation, biochemical characterization and detection of full length carotenoid cleavage in E. coli; the identification of new CCO activities and the finding that these enzymes are monooxygenases, not dioxygenases as proposed in the literature. Active enzymes from cyanobacteria were found to have four different cleavage activities: 15, 15'on full length carotenoids, 15,15' on apocarotenoid substrates, 9,10 (9',10') cleavage on full length carotenoids, and 9,10 on apocarotenoid substrates. An additional enzyme from an anoxygenic diazotroph was found to cleave the 15,15' double bond on full length carotenoids as well. In addition to carotenoid cleavage, bacterial enzymes capable of acting on alternative substrates (stilbene derivatives and farnesol) were examined. The discovery of stilbene cleavage by two enzymes from the soil bacterium Novosphingomonas aromaticivorans DSM12444 (NOV1 and 2) was beneficial because they afforded the opportunity to do mechanistic studies. The NOV enzymes were found to act through a stereospecific monooxygenase mechanism. The unique contributions of this work include the discovery of multiple active oxygenases within a single genome, improved protein expression conditions, methods for detecting full length carotenoid cleavage at the 15,15' double bond and the discovery that lignostilbene oxygenases act through a monooxygenase mechanism.

ISBN: 9780549468097Subjects--Topical Terms:

1017734
Biology, Microbiology.

Identification and characterization of bacterial carotenoid cleavage oxygenases.
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245 1 0 $a Identification and characterization of bacterial carotenoid cleavage oxygenases.
300 $a 222 p.
500 $a Adviser: Claudia Schmidt-Dannert.
500 $a Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0998.
502 $a Thesis (Ph.D.)--University of Minnesota, 2008.
520 $a Carotenoid cleavage oxygenases (CCOs) are non-heme iron oxygenases responsible for the oxidative cleavage of carotenoids, stilbenes and potentially other conjugated substrates. This enzyme family contains a non-canonical oxygenase active site because it is comprised of four histidines and a Fe2+. Cleavage of carotenoids by CCO enzymes has been observed in organisms from all kingdoms. The resulting cleavage products (known as apocarotenoids) have an array of biological activities (e.g. coloration, attraction of pollinators through aroma and flavors, and acting as hormones and signaling compounds). Carotenoid cleavage oxygenases were first described from metazoans and plants. Little was known about the distribution and function of CCO homologs in prokaryotes. This thesis describes the identification and functional characterization of 16 new CCO homologs from bacteria through the use of a combination of genome mining, biosynthetic pathway engineering and protein biochemistry. Findings of this thesis include the discovery of multiple active CCO paralogs in cyanobacteria; the development of methods for the isolation, biochemical characterization and detection of full length carotenoid cleavage in E. coli; the identification of new CCO activities and the finding that these enzymes are monooxygenases, not dioxygenases as proposed in the literature. Active enzymes from cyanobacteria were found to have four different cleavage activities: 15, 15'on full length carotenoids, 15,15' on apocarotenoid substrates, 9,10 (9',10') cleavage on full length carotenoids, and 9,10 on apocarotenoid substrates. An additional enzyme from an anoxygenic diazotroph was found to cleave the 15,15' double bond on full length carotenoids as well. In addition to carotenoid cleavage, bacterial enzymes capable of acting on alternative substrates (stilbene derivatives and farnesol) were examined. The discovery of stilbene cleavage by two enzymes from the soil bacterium Novosphingomonas aromaticivorans DSM12444 (NOV1 and 2) was beneficial because they afforded the opportunity to do mechanistic studies. The NOV enzymes were found to act through a stereospecific monooxygenase mechanism. The unique contributions of this work include the discovery of multiple active oxygenases within a single genome, improved protein expression conditions, methods for detecting full length carotenoid cleavage at the 15,15' double bond and the discovery that lignostilbene oxygenases act through a monooxygenase mechanism.
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