Nyob rau hauv tsab xov xwm no peb yuav xav txog ib qho ntawm cov kev hloov pauv ntawm cov piam thaj oxidation - txoj kev pentose phosphate. Kev sib txawv ntawm cov txheej txheem ntawm qhov tshwm sim no, txoj hauv kev rau nws txoj kev siv, qhov xav tau ntawm cov enzymes, qhov tseem ceeb ntawm cov roj ntsha thiab keeb kwm ntawm kev tshawb pom yuav raug tshuaj xyuas thiab piav qhia.
Qhia qhov tshwm sim
Txoj kev pentose phosphate yog ib txoj hauv kev uas C6H12O6 (glucose) yog oxidized. Muaj cov theem oxidizing thiab tsis-oxidizing.
txheej txheem txheej txheem sib npaug:
3glucose-6-phosphate+6NADP-à3CO2+6(NADPH+H-) + 2 fructose-6-phosphate + glyceraldehyde-3-phosphate.
Tom qab dhau los ntawm txoj kev oxidative pentose phosphate, hyceraldehyde-3-phosphate molecule hloov mus rau pyruvate thiab tsim 2 molecules ntawm adenosine triphosphoric acid.
Tsiaj txhu thiab cov nroj tsuag ntawm lawv cov subunits muaj ntau qhov kev faib tawm ntawm qhov tshwm sim no, tab sis cov kab mob siv nws tsuas yog ua cov txheej txheem pabcuam xwb. Tag nrho cov enzymes ntawm txoj kev yog nyob rau hauv cellular cytoplasm nyob rau hauv cov tsiaj thiab cov nroj tsuag kab mob. Tsis tas li ntawd, cov tsiaj muaj cov tshuaj noKuj tseem nyob hauv EPS, thiab cov nroj tsuag hauv plastids, tshwj xeeb hauv chloroplasts.
Txoj hauv kev pentose phosphate ntawm cov piam thaj oxidation zoo ib yam li cov txheej txheem ntawm glycolysis thiab muaj txoj hauv kev evolutionary ntev heev. Tej zaum, nyob rau hauv cov dej ib puag ncig ntawm Archaean, ua ntej lub ntsej muag ntawm lub neej nyob rau hauv nws cov niaj hnub kev xav, kev tshwm sim uas yog precisely ntawm ib tug pentose phosphate xwm, tab sis lub catalyst rau xws li ib tug voj voog tsis yog ib tug enzyme, tab sis hlau ions.
Hom kev tawm tsam uas twb muaj lawm
Raws li tau sau tseg ua ntej, txoj hauv kev pentose phosphate txawv ob theem, lossis cycles: oxidative thiab non-oxidative. Yog li ntawd, ntawm oxidative ib feem ntawm txoj kev, C6H12O6 yog oxidized los ntawm qabzib-6-phosphate rau ribulose-5-phosphate, thiab thaum kawg NADPH raug txo. Lub ntsiab lus ntawm cov theem uas tsis yog-oxidative yog los pab rau cov synthesis ntawm pentose thiab suav nrog koj tus kheej hauv kev hloov pauv hloov pauv ntawm 2-3 carbon "thooj". Tsis tas li ntawd, kev hloov pauv ntawm pentoses mus rau lub xeev ntawm hexoses tuaj yeem rov tshwm sim, uas yog tshwm sim los ntawm ntau dhau ntawm pentose nws tus kheej. Cov catalysts koom nrog hauv txoj kev no tau muab faib ua 3 lub tshuab enzymatic:
- dehydro-decarboxylation system;
- isomerizing yam system;
- ib lub cev tsim los kho cov suab thaj.
Reactions nrog thiab tsis muaj oxidation
Cov oxidative ntawm txoj kev yog sawv cev los ntawm cov kab zauv hauv qab no:
Glucose6phosphate+2NADP++H2Oàribulose5phosphate+2 (NADPH+H+)+CO2.
BNyob rau hauv cov kauj ruam uas tsis yog-oxidative, muaj ob catalysts nyob rau hauv daim ntawv ntawm transaldolase thiab transketolase. Lawv ua kom tawg ntawm C-C daim ntawv cog lus thiab kev hloov pauv ntawm cov paib ntawm cov saw hlau uas tau tsim los ntawm qhov kev tawg no. Transketolase siv coenzyme thiamine pyrophosphate (TPP), uas yog vitamin ester (B 1) ntawm hom diphosphorus.
daim ntawv dav dav ntawm theem sib npaug hauv qhov tsis yog oxidative version:
3 ribulose5phosphateà1 ribose5phosphate + 2 xylulose5phosphateà2 fructose6phosphate +glyceraldehyde3phosphate.
Qhov kev hloov pauv oxidative ntawm txoj hauv kev tuaj yeem pom thaum NADPH siv los ntawm lub xovtooj, lossis lwm yam lus, thaum nws mus rau tus qauv txoj haujlwm hauv nws daim ntawv tsis txo qis.
Kev siv cov tshuaj tiv thaiv glycolysis lossis txoj hauv kev piav qhia nyob ntawm tus nqi ntawm NADP concentration+ hauv cov tuab ntawm cytosol.
Path cycle
Cov ntsiab lus tau txais los ntawm kev txheeb xyuas qhov sib npaug ntawm txoj hauv kev uas tsis yog oxidative variant, peb pom tias pentoses tuaj yeem rov qab los ntawm hexoses mus rau qabzib monosaccharides siv pentose phosphate txoj kev. Tom qab hloov pauv ntawm pentose rau hexose yog pentose phosphate cyclic txheej txheem. Txoj kev nyob rau hauv kev xav thiab tag nrho nws cov txheej txheem yog concentrated, raws li txoj cai, nyob rau hauv cov ntaub so ntswg adipose thiab lub siab. Tag nrho qhov sib npaug tuaj yeem piav qhia raws li:
6 qabzib-6-phosphate+12nadp+2H2Oà12(NADPH+H+)+5 glucose-6-phosphate+6 CO2.
Non-oxidative hom pentose phosphate txoj kev
Cov kauj ruam uas tsis yog oxidative ntawm pentose phosphate txoj kev tuaj yeem rov kho cov piam thaj yam tsis muajKev tshem tawm CO2, uas tuaj yeem ua tau vim yog lub zog enzymatic (nws rov kho cov suab thaj thiab glycolytic enzymes uas hloov cov piam thaj-6-phosphate rau glyceraldehyde-3-phosphate).
Thaum kawm txog cov metabolism ntawm cov lipids tsim cov poov xab (uas tsis muaj phosphofructokinase, uas tiv thaiv lawv los ntawm oxidizing C6H12O6 monosaccharides siv glycolysis), nws tau pom tias cov piam thaj hauv cov nyiaj ntawm 20% dhau oxidation siv pentose phosphate txoj kev, thiab qhov seem 80% raug kho dua tshiab ntawm qhov tsis yog-oxidative theem ntawm txoj kev. Tam sim no, cov lus teb rau lo lus nug ntawm yuav ua li cas raws nraim 3-carbon compound tsim, uas tsuas yog tsim tau thaum lub sij hawm glycolysis, tseem tsis paub.
Kev ua haujlwm rau cov kab mob muaj sia
Tus nqi ntawm pentose phosphate txoj hauv kev hauv cov tsiaj thiab cov nroj tsuag, nrog rau cov kab mob yuav luag zoo ib yam Txhua lub hlwb ua cov txheej txheem no txhawm rau tsim cov kev txo qis ntawm NADPH, uas yuav siv los ua hydrogen pub rau hauv txo hom tshuaj tiv thaiv thiab hydroxylation. Lwm txoj haujlwm yog muab cov hlwb nrog ribose-5-phosphate. Txawm hais tias muaj tseeb tias NADPH tuaj yeem tsim los ntawm oxidation ntawm malate nrog kev tsim ntawm pyruvate thiab CO2, thiab nyob rau hauv cov ntaub ntawv ntawm dehydrogenation ntawm isocitrate, zus tau tej cov reductive sib npaug tshwm sim vim pentose phosphate txheej txheem. Lwm qhov nruab nrab ntawm txoj kev no yog erythrose-4-phosphate, uas, ua rau muaj kev sib xyaw nrog phosphoenolpyruvates, pib tsim cov tryptophan, phenylalanine thiab tyrosines.
Kev ua haujlwmTxoj kev pentose phosphate yog pom nyob rau hauv cov tsiaj nyob rau hauv lub cev ntawm lub siab, cov qog mammary thaum lub sij hawm lactation, testes, adrenal cortex, raws li zoo raws li nyob rau hauv erythrocytes thiab adipose ntaub so ntswg. Qhov no yog vim muaj cov nquag hydroxylation thiab rov tsim cov tshuaj tiv thaiv, piv txwv li, thaum lub sij hawm synthesis ntawm fatty acids, kuj tau pom thaum lub sij hawm kev puas tsuaj ntawm xenobiotics nyob rau hauv daim siab cov ntaub so ntswg thiab lub active oxygen daim ntawv nyob rau hauv erythrocyte hlwb thiab lwm yam ntaub so ntswg. Cov txheej txheem zoo li no ua rau muaj kev thov siab rau ntau yam sib npaug, suav nrog NADPH.
Cia peb xav txog qhov piv txwv ntawm erythrocytes. Nyob rau hauv cov molecules, glutathione (tripeptide) yog lub luag hauj lwm rau lub neutralization ntawm active oxygen daim ntawv. Cov tshuaj no, dhau mus rau oxidation, hloov hydrogen peroxide rau hauv H2O, tab sis qhov kev hloov pauv ntawm glutathione mus rau qhov kev hloov pauv txo tau nyob rau hauv lub xub ntiag ntawm NADPH + H+ . Yog tias lub cell muaj qhov tsis xws luag hauv qabzib-6-phosphate dehydrogenase, tom qab ntawd kev sib sau ntawm hemoglobin txhawb nqa tuaj yeem pom, vim tias cov erythrocyte poob nws cov plasticity. Lawv lub cev ua haujlwm tsuas yog ua tau nrog kev ua haujlwm tag nrho ntawm pentose phosphate txoj hauv kev.
Cov nroj tsuag hloov pauv pentose phosphate txoj hauv kev muab lub hauv paus rau theem tsaus ntuj ntawm photosynthesis. Tsis tas li ntawd, qee pawg nroj tsuag feem ntau nyob ntawm qhov tshwm sim, uas tuaj yeem ua rau, piv txwv li, kev hloov pauv sai ntawm cov suab thaj, thiab lwm yam.
Lub luag haujlwm ntawm pentose phosphate txoj hauv kev rau cov kab mob nyob hauv cov kev cuam tshuam ntawm gluconate metabolism. Cyanobacteria siv cov txheej txheem no los ntawm kev tsim txiaj ntawmtsis muaj lub voj voog Krebs tag nrho. Lwm cov kab mob siv qhov tshwm sim no kom nthuav tawm ntau cov suab thaj rau oxidation.
Cov txheej txheem kev cai
Txoj kev cai ntawm pentose phosphate txoj hauv kev nyob ntawm qhov muaj qhov xav tau ntawm cov piam thaj-6-phosphate los ntawm lub xovtooj ntawm tes thiab qib ntawm cov concentration ntawm NADP + hauv cytosol kua. Nws yog ob yam no uas yuav txiav txim siab seb cov molecule uas tau hais los saum no yuav nkag mus rau hauv cov tshuaj tiv thaiv glycolysis lossis rau hauv pentose phosphate hom txoj kev. Qhov tsis muaj cov neeg txais hluav taws xob yuav tsis tso cai rau thawj kauj ruam ntawm txoj kev mus. Nrog rau kev hloov pauv sai ntawm NADPH rau NADPH+, qib siab ntawm tom kawg nce. Glucose 6 phosphate dehydrogenase yog allosterically stimulated thiab thiaj li ua kom cov piam thaj 6 phosphate flux ntawm pentose phosphate hom pathway. Kev qeeb ntawm kev noj NADPH ua rau txo qis hauv qib NADP+, thiab qabzib-6-phosphate raug pov tseg.
History data
Txoj hauv kev pentose phosphate pib nws txoj kev tshawb fawb vim qhov tseeb tias kev saib xyuas tau them rau qhov tsis muaj kev hloov pauv hauv cov piam thaj los ntawm cov glycolysis inhibitors. Yuav luag ib txhij nrog qhov xwm txheej no, O. Warburg tau tshawb pom NADPH thiab pib piav qhia txog oxidation ntawm qabzib-6-phosphates rau 6-phosphogluconic acids. Tsis tas li ntawd, nws tau ua pov thawj tias C6H12O6, cim nrog isotopes 14 C (cim raws li C-1), hloov mus rau 14 CO2 kuj nrawm dua. qhov no tib yam molecule, tab sis sau npe C-6. Qhov no yog qhov qhia txog qhov tseem ceeb ntawm cov txheej txheem ntawm kev siv cov piam thaj thaum lub sijhawmkev pab ntawm lwm txoj kev. Cov ntaub ntawv no tau luam tawm los ntawm I. K. Gansalus xyoo 1995.
Zoo kawg
Thiab yog li ntawd, peb pom tias txoj hauv kev hauv kev txiav txim siab yog siv los ntawm cov hlwb ua lwm txoj hauv kev ntawm oxidizing qabzib thiab muab faib ua ob txoj hauv kev uas nws tuaj yeem ua mus. Qhov tshwm sim no tau pom nyob rau hauv txhua hom kab mob multicellular thiab txawm nyob rau hauv ntau yam kab mob. Kev xaiv ntawm txoj kev oxidation nyob ntawm ntau yam, muaj qee yam tshuaj nyob rau hauv lub cell thaum lub sij hawm cov tshuaj tiv thaiv.
