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'Cytochrome P 450' in keywords Facet   Publication Year 1990  [X]
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1Author    W. Häberle, H. G. Ruler, Ph Dutkowski, D. Müller-EnochRequires cookie*
 Title    Light-Induced Activation and Synchronization of the Cytochrome P-450 Dependent Monooxygenase System  
 Abstract    The light-induced enhancement o f the 7-ethoxycoumarin-O-deethylase activity was m eas­ ured in a reconstituted system, consisting o f the enzyme P-450pb_b and the N A D P H -cyto-chrome P-450 reductase. The relative increase o f the activity was about 15%. It is shown that the product release process is accelerated by light. The phases o f the catalytic cycle o f 2 x 1012 protein complexes were locked by periodic application o f light pulses (0.1 s duration, 1.32 s repetition time, and 3 9 0 -4 7 0 nm, 0.27 joule/nm ol P-450). More than 80% o f the active recon­ stituted enzyme com plexes (= "molecular machines") worked in phase after a few light pulses. The phase relation continued even after switching o ff the light pulses. The catalytic cycle time was 1.54 s, giving a turnover number o f 39 min-1. The turnover number, as determined from the enzyme activity under optimum conditions, was 39 m in-1. Due to the dissociation constant o f the P-450pb_b:N A D P H -P -450 reductase complexes [3] only 24% o f the proteins were in the active (= working) state under the conditions used. The lifetime o f this complexes is larger than 6 s since more than 4 cycles o f the free running enzyme can be observed. This is the first report, that all catalytic active complexes in the test tube can be synchronized by an external light source, if the right repetition time o f the pulses is chosen, so that all these "molecular machines" work in phase. 
  Reference    Z. Naturforsch. 45c, 273 (1990); received September 14/November 28 1989 
  Published    1990 
  Keywords    Cytochrome P-450, Light-Induced Activation and Synchronization, Catalytic Cycle Time 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0273.pdf 
 Identifier    ZNC-1990-45c-0273 
 Volume    45 
2Author    DonaldE. Moreland, FrederickT. Corbin, WilliamP. Novitzky, CarolE. Parker, KennethB. TomerRequires cookie*
 Title    Metabolism of Metolachlor by a Microsomal Fraction Isolated from Grain Sorghum ( Sorghum bicolor) Shoots  
 Abstract    A microsomal fraction isolated from the shoots of 3-to 4-day-old, dark-grown, grain sor­ ghum (Sorghum bicolor cv. Funk G 522 D R) seedlings was characterized. The preparations had a cytochrome P-450 content that varied from approximately 90 to 150 pmol P-450/mg protein with cytochrome P-420 varying from 0 to 3% of the P-450 content. Type I difference spectra were formed with cinnamic acid and metolachlor, and a type II spectrum was formed with tetcyclacis. In short-term assays with [14C]metolachlor as substrate, the preparations produced a single time-dependent product that separated on silica gel TLC plates developed in benzene/ acetone (2:1, v/v). R F values for metolachlor and the metabolite were approximately 0.70 and 0.48, respectively. The microsomal reaction required N A D PH and oxygen, and was inhibited by carbon monoxide, with the inhibition being partially reversed by actinic light. Compounds known to inhibit the activity of cytochrome P-450 monooxygenases (piperonyl butoxide, tet­ cyclacis, and tridiphane) also prevented formation of the metabolite. Identity of the metabolite was confirmed by TLC and positive ion thermospray LC/MS to be 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-hydroxy-l-methylethyl)acetamide. Hence, the reaction catalyzed by the sorghum microsomes involved O-demethylation of the methoxypropyl side chain of meto­ lachlor. 
  Reference    Z. Naturforsch. 45c, 558—564 (1990); received November 9 1989 
  Published    1990 
  Keywords    Microsomes, Metolachlor, Cytochrome P-450, Mixed Function Oxidase, Herbicide Metabolism 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0558.pdf 
 Identifier    ZNC-1990-45c-0558 
 Volume    45