Synthesis Of Acetyl-CoA Flashcards
What is the citric acid cycle
Is a pathway to obtain energy from carbohydrates, fatty acids, amino acids. These are broken down into acetyl-coA and then oxidized
The enzymes of the TCA are where
In the matrix of the mitochondria
What is pyruvate dehydrogenase and what are it’s subunits
It is a multienzyme complex made of : E1 (pyruvate dehydrogenase), E2 (dihydrolipoyl transacetylase), E3 (dihydrolipoyl dehydrogenase), E4 (E3BP)
What makes up the central core and outer shell of pyruvate dehydrogenase
Central core is made of 60 E2 subunits (which have a dodecahedral symmetry) combine with 12 E3BP. The outer shell is made of 9 E3 subunits (are homodimers) partly embedded in the E2 core and 45E1 heterotetramers from a shell around the E2/E3BP core
What are cofactprs of the pyruvate dehydrogenase enzyme
3 prosthetic groups : TPP, Lipoamide, FAD
2 cosubstrates : coA, NAD+
Where is TPP, function?
Bound to E1, decarboxylates pyruvate, yields a hydroxyethyl TPP carbanion
Where is Lipoamide and what’s it’s function
Linked to Lys on E2, it accepts the hydroxyethyl carbanion group as an acetyl group
Where is coA and what is it’s function
It’s a substrate for E2, accepts the acetyl group from lipoamide
Where is FAD and what is it’s function
Is bound to E3, it is reduced by lipoamide
Where is NAD+ and what is it’s function
It is reduced by FADH2
The active form of thiamine is TPP, what are it’s functions
Needed for pyruvate decarboxylase in alcohol fermentation, for transketolase in PPP, in decarboxylation of pyruvate , synthesis of Ach and GABA and leu and Val
The constituents of acetyl coA are
3’-phosphoadenosine diphosphate, pantothenic acid, beta- mercapto ethylamine, acetyl group
Riboflavin is made of
D-ribitol and isoalloxazine
FMN is made of
Isoallaxozanine, D-ribitol, phosphate group
FAD is made of
D-ribitol, isoallaxozanine, phosphate group, AMP
List the specifics between hydride ion transfer when going from the oxidized form to the reduced form of nicotinamide
The N+ attracts electrons so it makes the transfer of H+ easier, the H+ addition site is prochiral, the transfer is steroespecific
What are the components and individual functions of the subunits of the pyruvate dehydrogenase complex and how they help the formation of acetyl coA
E1- contains TPP and catalyses reaction 1+2 , E2- contains lipoamide and catalyses reaction 3, E3- contains FAD with a SS in a redox center and catalyses reaction 4 and 5
What is reaction 1
The pyruvate dehydrogenase (E1) decarboxylates pyruvate and forms hydroxyethyl TPP
What is reaction 2
The Lipoamide accepts the hydroxyethyl group and the hydroxyethyl carbanion is oxidized into acetyl and the Lipoamide disulfide bonds are reduced
What is reaction 3
The dihydrolipoyl transacetylase catalyses the transfer of the acetyl from the Lipoamide onto coA. This is a transesterification reaction
What is reaction 4
Dihydrolipoyl dehydrogenase oxidizes dihydrolipoamide by reducing the S-S bond into 2 S-H bonds in the FAD redox center, this is a disulfide exchange
What is reaction 5
It is catalysed by E3, the 2 S-H bonds in the FAD redox center are reoxidized into S-S bonds, FAD gives electrons to NAD+ forming NADH
What is the lipoyllysyl arm
It is a structure of the E2 subunits of the pyruvate dehydrogenase complex, it is used to transfer intermediates
ATP synthesis happens in the
inner mitochondrial membrane
PDH is allosterically inhibited by
acetyl coA, NADH, ATP
PDH is allosterically enhanced by
AMP
PDH is covalently inhibited by
pyruvate DH kinase, WHICH IS stopped by Ca2+, pyruvate, ADP and encouraged by NADH and acetyl coA
PDH is covalently encouraged by
pyruvate DH phosphatase, which is encouraged by insulin, Ca2+, Mg2+
