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23 Cards in this Set
- Front
- Back
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Explain PDH
(eqn) what does it do |
Pyruvate dehydrogenase:
pyruvate + NAD + CoA --> Acetyl~CoA + NADH + H + CO2 it is a multienzyme complex: this allows the efficient transfer of intermediates b/w active sites, interm usually cov linked to enz |
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PDH cont'd
structure name the catalytic cofactor name the stoichiometric cofactor |
catalytic cofactor: coenz-prosthetic group FAD TPP(thiamine pyrophosphate) and lipoic acid)
Stoichiometric cofactor: coenz-cosubstrate - NAD CoA 2 stoichiometric coenz-cosubstrates (NAD CoA) 3 coenzy prosthetic groups 3 distinct enz 2 other enz regulate activity of PDH complex |
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where does PDH cycle occur?
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in the mitochondrial matrix
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what does PDH do in a general sense
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converts pyruvate from cytosol into Acetyl CoA for entry into TCA cycle
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explain, using the different enz's of PDH, how it converts pyruvate into Acetyl CoA
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pyruvate is decarboxylated by TPP in E1
oxidation by lipoic acid in E2(causing transfer of acetyl group to CoA) reoxidation of lipoic acid by FAD (b/cms FADH) FADH is then converted back to FAD via 2NAD |
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in PDH, give the names for E1 E2 and E3
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E1: pyruvate dehydrogenase(pyruvate decarboxylase)
E2: dihydrolipoyl transacetylase (lysine chain acts as a swinging arm to transfer e from E1 to E3) E3: dihydrolipoyl dehydrogenase SEE www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/pdc/pdc.html |
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In PDH deficiency, why is lacticacidemia an expected finding?
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??
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Control of PDH
very important explain covalent regulation |
most important: inhibition through phosphorylation of E1
Covalent regulation: Kinase: INACTIVATES stim by ATP(uses it) NADH and AcetylCoa inhib by pyruvate Phosphatase: ACTIVATES activated by Ca (Ca released when ATP is utilized) therefore PDH is upregulated in response to energy deprivation |
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name two ways acetylCoA is produced
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PDH and beta-oxidation of fatty acids
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anaplerotic reactions
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rxns that generate TCA intermediates outside of the TCA cycle itself, this is necessary b/c most of the enzymes are free floating in the matrix space and can be used up in other pathways
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explain the initiating step in the TCA cycle and what makes it irreversible
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citrate synthase catalyzes the condensation of acetylCoA with oxaloacetate to form citrate
hydrolysis of the thioester bond of CoA makes it irreversible! |
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Which steps in TCA produce NADh/FADH2
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3 produce NADH, IDH alpha-ketoglutarate dehydrogenase, malate dehydrogenase
1 produces FADH2, succinate dehydrogenase |
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list the names of the TCA cycle intermediates in order
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Can I Keep Selling Sex For Money Officer?
citrate isocitrate alpha-ketoglutarate succinyl CoA succinate fumarate l-malate oxaloacetate |
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what enzyme is embedded in the inner mitochondrial membrane?
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succinate dehydrogenase
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what is the name of reactions that generate TCA cycle intermediates from outside the cycle itself?
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anaplerotic reactions
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what, besides hydrolysis of thioester bond of CoA is important about the initiating step?
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enzyme-bound intermediate is formed. Citrate synthase
Citroyl-SCoA Free state, citrate synthase binds oxaloacetate first causes a change and then binds acetyl CoA so that Acetyl CoA isnt wasted by changing into citric acid |
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what other reactions form enz-intermediates
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aconitase enz forms cis-aconitate before forming isocitrate
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explain competitive product inhibition of PDH
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acetyl CoA competitively inhibits E2(binds active site?)
NADH competitively inhibits E3 |
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aconistase
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citrate to isocitrate through cis-aconitase
relocation of OH prepares it for IDH |
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isocitrate dehydrogenase
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isocitrate to alpha-ketoglutarate through the intermediate oxalosuccinate
forms NADH and CO2 |
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alpha-ketoglutarate dehydrogenase
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alpha-ketoglutarate to succinyl CoA
produces CO2 using CoASH produces NADH |
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Succinyl CoA synthetase (Succinyl Thiokinase)
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reversible? pg 390
succinyl CoA-> Succinate produces coash from Pi makes GTP COUPLING - GTP production is coupled to the high energy bond in succinyl coa made previously from alpha keto glutarate, succinyl CoA is the intermediate SPECIFICALLY Succinyl CoA -> succinyl phosphate -> succinate it's succinyl phosphate to succinate that generates GTP, so succinyl phosphate is the intermediate in that reaction |
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where does most of the respiratory CO2 come from?
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IDH alpha KDH and PDH
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