RuBisCO

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(Reakcije encima)
Current revision (16:33, 26 January 2011) (view source)
 
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== Viri ==
== Viri ==
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Plant phisiology online: Modulation of RuBisCO-activase [http://4e.plantphys.net/image.php?id=107]
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#Plant phisiology online: Modulation of RuBisCO-activase [http://4e.plantphys.net/image.php?id=107]
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PNAS of USA: activation of RuBisCO [http://www.pnas.org/content/97/24/12937/F1.expansion.html]
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#PNAS of USA: activation of RuBisCO [http://www.pnas.org/content/97/24/12937/F1.expansion.html]
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Wikipedia: RuBisCO [http://en.wikipedia.org/wiki/RuBisCO]
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#Wikipedia: RuBisCO [http://en.wikipedia.org/wiki/RuBisCO]
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Plant Biology [http://www.amazon.ca/Plant-Biology-Alison-M-Smith/dp/0815340257]
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#Plant Biology [http://www.amazon.ca/Plant-Biology-Alison-M-Smith/dp/0815340257]
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Molecular cell biology [http://www.amazon.com/Molecular-Cell-Biology-Lodish/dp/0716776014]
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#Molecular cell biology [http://www.amazon.com/Molecular-Cell-Biology-Lodish/dp/0716776014]
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[http://www.google.si/imgres?imgurl=http://www.biologie.uni-hamburg.de/b-online/fo24_1/1rxos.gif&imgrefurl=http://www.biologie.uni-hamburg.de/b-online/fo24_1/e1rxoe.htm&usg=__84AqQACceu600x_3OJ4BNgE6tDQ=&h=687&w=672&sz=115&hl=sl&start=0&sig2=Iwa6l2xGnJkr50W6xbQVuw&zoom=1&tbnid=mZ1v7TWipj1k7M:&tbnh=136&tbnw=133&ei=jkIFTaSUIImztAbk8tHiCQ&prev=/images%3Fq%3DRubisco%26hl%3Dsl%26client%3Dfirefox-a%26rls%3Dorg.mozilla:sl:official%26biw%3D1366%26bih%3D576%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=1103&vpy=274&dur=2346&hovh=227&hovw=222&tx=140&ty=170&oei=jkIFTaSUIImztAbk8tHiCQ&esq=1&page=1&ndsp=21&ved=1t:429,r:20,s:0]
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#[http://www.google.si/imgres?imgurl=http://www.biologie.uni-hamburg.de/b-online/fo24_1/1rxos.gif&imgrefurl=http://www.biologie.uni-hamburg.de/b-online/fo24_1/e1rxoe.htm&usg=__84AqQACceu600x_3OJ4BNgE6tDQ=&h=687&w=672&sz=115&hl=sl&start=0&sig2=Iwa6l2xGnJkr50W6xbQVuw&zoom=1&tbnid=mZ1v7TWipj1k7M:&tbnh=136&tbnw=133&ei=jkIFTaSUIImztAbk8tHiCQ&prev=/images%3Fq%3DRubisco%26hl%3Dsl%26client%3Dfirefox-a%26rls%3Dorg.mozilla:sl:official%26biw%3D1366%26bih%3D576%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=1103&vpy=274&dur=2346&hovh=227&hovw=222&tx=140&ty=170&oei=jkIFTaSUIImztAbk8tHiCQ&esq=1&page=1&ndsp=21&ved=1t:429,r:20,s:0]
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[http://www.google.si/imgres?imgurl=http://guweb2.gonzaga.edu/faculty/cronk/biochem/images/rubisco-rxn.gif&imgrefurl=http://guweb2.gonzaga.edu/faculty/cronk/biochem/R-index.cfm%3Fdefinition%3DR&usg=__1_KCzooGgLHObAXiYICktz0FXq8=&h=251&w=710&sz=8&hl=sl&start=0&sig2=cTG5hpDyoYWr7LhpUE0WJw&zoom=1&tbnid=i0ZThI5ywkCV8M:&tbnh=74&tbnw=208&ei=EEsFTcDvDIvqOfqBxaYB&prev=/images%3Fq%3Drubisco%2Breaction%26hl%3Dsl%26client%3Dfirefox-a%26rls%3Dorg.mozilla:sl:official%26biw%3D1366%26bih%3D576%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=83&vpy=352&dur=3420&hovh=133&hovw=378&tx=224&ty=111&oei=cUoFTcyIMJDxsgaM3qHtCQ&esq=4&page=1&ndsp=18&ved=1t:429,r:12,s:0]
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#[http://www.google.si/imgres?imgurl=http://guweb2.gonzaga.edu/faculty/cronk/biochem/images/rubisco-rxn.gif&imgrefurl=http://guweb2.gonzaga.edu/faculty/cronk/biochem/R-index.cfm%3Fdefinition%3DR&usg=__1_KCzooGgLHObAXiYICktz0FXq8=&h=251&w=710&sz=8&hl=sl&start=0&sig2=cTG5hpDyoYWr7LhpUE0WJw&zoom=1&tbnid=i0ZThI5ywkCV8M:&tbnh=74&tbnw=208&ei=EEsFTcDvDIvqOfqBxaYB&prev=/images%3Fq%3Drubisco%2Breaction%26hl%3Dsl%26client%3Dfirefox-a%26rls%3Dorg.mozilla:sl:official%26biw%3D1366%26bih%3D576%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=83&vpy=352&dur=3420&hovh=133&hovw=378&tx=224&ty=111&oei=cUoFTcyIMJDxsgaM3qHtCQ&esq=4&page=1&ndsp=18&ved=1t:429,r:12,s:0]
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[http://www.google.si/imgres?imgurl=http://www.pnas.org/content/97/24/12937/F1.large.jpg&imgrefurl=http://www.pnas.org/content/97/24/12937/F1.expansion.html&usg=__2MLRb0rTyE8ir8N2Y5phnnoc7V8=&h=1114&w=1280&sz=147&hl=sl&start=0&sig2=EVIJt5n2ah7rTQAplwLE8Q&zoom=1&tbnid=4yI7SRf_odxvSM:&tbnh=135&tbnw=154&ei=pUsFTc7SJM_qOY2B4aYB&prev=/images%3Fq%3Drubisco%2Bactivation%26hl%3Dsl%26client%3Dfirefox-a%26rls%3Dorg.mozilla:sl:official%26biw%3D1366%26bih%3D576%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=125&vpy=70&dur=291&hovh=209&hovw=241&tx=120&ty=73&oei=jEsFTbaQIpKBswazwIXzCQ&esq=11&page=1&ndsp=21&ved=1t:429,r:0,s:0]
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#[http://www.google.si/imgres?imgurl=http://www.pnas.org/content/97/24/12937/F1.large.jpg&imgrefurl=http://www.pnas.org/content/97/24/12937/F1.expansion.html&usg=__2MLRb0rTyE8ir8N2Y5phnnoc7V8=&h=1114&w=1280&sz=147&hl=sl&start=0&sig2=EVIJt5n2ah7rTQAplwLE8Q&zoom=1&tbnid=4yI7SRf_odxvSM:&tbnh=135&tbnw=154&ei=pUsFTc7SJM_qOY2B4aYB&prev=/images%3Fq%3Drubisco%2Bactivation%26hl%3Dsl%26client%3Dfirefox-a%26rls%3Dorg.mozilla:sl:official%26biw%3D1366%26bih%3D576%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=125&vpy=70&dur=291&hovh=209&hovw=241&tx=120&ty=73&oei=jEsFTbaQIpKBswazwIXzCQ&esq=11&page=1&ndsp=21&ved=1t:429,r:0,s:0]
== Povezave ==
== Povezave ==
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Manipulation of RuBisCO:the amount, activity, function and regulation [http://jxb.oxfordjournals.org/content/54/386/1321.full]
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#Manipulation of RuBisCO:the amount, activity, function and regulation [http://jxb.oxfordjournals.org/content/54/386/1321.full]
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Orderly Disposition of Heterogeneous Small Subunits in D-Ribulose-1,5-bisphosphate Carboxylase/Oxygenase from Spinach [http://www.jbc.org/content/271/43/26449.full]
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#Orderly Disposition of Heterogeneous Small Subunits in D-Ribulose-1,5-bisphosphate Carboxylase/Oxygenase from Spinach [http://www.jbc.org/content/271/43/26449.full]
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[[Category:LEX]]

Current revision

RuBisCO je okrajšava za ribulozo-1,5-bifosfat-karboksilaza/oksigenaza. Je encim, ki se nahaja v stromi kloroplasta in sodeluje v temotnih reakcijah pri fotosintezi/ v Calvinovem ciklu. Predstavlja 15% vseh proteinov v kloroplastu in velja za enega najbolj zastopanih encimov na Zemlji.


Contents

Zgradba encima

RuBisCO je sestavljen iz šestnajstih podenot- osmih velikih in osmih malih, ki imajo skupno molsko maso okoli 540kDa. Velika podenota L z molsko maso 55kDa je zapisana v plastidni DNA kloroplasta, kjer se tudi sintetizira. V njej so vezavna mesta za substrat. Mala podenota S je zapisana v jedrni DNA, sintetizira se v citoplazmi in skozi membrano vstopa v kloroplast. Njena molska masa znaša 13kDa. (slika: zgradba RuBisCO)


Reakcije encima

RuBisCO se lahko obnaša kot karboksilaza ali oksigenaza, saj lahko sintetizira sadkorno molekulo RuBP (ribuloza-1,5-bifosfat) tako s CO2 kot tudi z O2. Glede na vrsto vezave plinastega substrata ločimo dva tipa reakcij:

-vezava ogljika (CO2) 
-fotorespiracija (vezava O2)

Pri vezavi CO2 poteka reakcija med RuBP in CO2 do nastanka 6C vmesnega produkta (2-keto-2-karboksiarabinitol-1,5-bifosfat), ki je neobstojen in zato razpade v dve molekuli 3-fosfoglicerata. (slika: potek reakcije)

Pri fotorespiraciji pride do vezave molekule O2 na RuBP, pri čemer nastaneta molekuli 3-fosfoglicerata in 2-fosfoglicerata. RuBisCO ima manjšo afiniteto do vezave s kisikom, saj tako poteče le 25% vseh reakcij.

Aktivnost encima

V aktivno fazo RuBisCO preide s pomočjo RuBisCO aktivaze. Najprej se na encim s pomočjo ATP vežeta aminokislina lizin in RuBP, ki povzroči komformcijske spremembe im nato izstopi iz encima. Na lizin se veže CO2, ki se reducira v COO-, nanj pa kofaktor Mg2+2, ki povzroči aktivacijo encima. Na encimsko aktivnost vplivajo tudi pH, ki je podnevi zaradi svetlobnih reakcij fotosinteze 8, ponoči pa pade na 7 in deaktivira encim, pa tudi koncentracija kofaktorja Mg2+2, CO2. (slika: aktivacija encima)

RuBisCO je počasen encim (sintetizira 3-5 reakcij na min) in je glavni določevalec hitrosti temotnih reakcij.


Viri

  1. Plant phisiology online: Modulation of RuBisCO-activase [1]
  2. PNAS of USA: activation of RuBisCO [2]
  3. Wikipedia: RuBisCO [3]
  4. Plant Biology [4]
  5. Molecular cell biology [5]
  6. [6]
  7. [7]
  8. [8]


Povezave

  1. Manipulation of RuBisCO:the amount, activity, function and regulation [9]
  2. Orderly Disposition of Heterogeneous Small Subunits in D-Ribulose-1,5-bisphosphate Carboxylase/Oxygenase from Spinach [10]
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